CANARD-WING INTERACTIONS IN SUBSONIC FLOW *

Transcription

1 IJST, Transactions o Mechanical Engineering, Vol. 37, No. M2, pp Printed in The Islamic Republic o Iran, 213 Shiraz University CANARD-WING INTERACTIONS IN SUBSONIC FLOW * S. SAMIMI 1, ** A. R. DAVARI 2 AND M. R. SOLTANI 3 1, 2 Dept. o Mech. and Aerospace Eng., Science and Research Branch, Islamic Azad University, Tehran, I. R. o Iran salva_samimi@yahoo.com 3 Dept. o Aerospace Eng., Shari University o Technology, Tehran, I. R. o Iran Abstract Extensive subsonic wind tunnel tests were conducted on a coplanar wing-canard coniguration at various angles o attack. In these experiments, a 6 swept canard was placed upstream o a 6 swept main delta wing. This paper deals with the distribution o mean and luctuating pressure coeicients on the upper suraces o both the canard and the wing immersed in a variety o angles o attack. According to the results, presence o canard postpones the vortex ormation and growth on the wing to higher angles o attack compared to the canard-o case. Due to the canard downwash ield, the wing operates at lower eective angles o attack and thereore, its vortex breakdown is delayed. The spectral analysis o the unsteady pressure on both the canard and the wing show the existence o narrow, dominant requency band containing the majority o the luctuation energy. This requency band is believed to be the natural requency o the leading edge vortex. The results show that the dominant requency o the wing vortex is lower than that o the canard having the same sweep angle as the wing, which is an indication o the wing vortex attenuation due to canard downwash ield. Keywords Canard, delta wing, pressure power spectrum, leading edge vortex 1. INTRODUCTION The use o canards in advanced aircrat or control enhancement and or improved aerodynamic perormance is a topic o continued interest and research. In addition to providing maneuver control and trim, the inluence o canards on wing aerodynamics oten increases maximum lit and decreases trim drag. In many canard-conigured aircrat, the main beneits o canards are realized during maneuver or other dynamic conditions. For close-coupled canards, the aerodynamierormance associated with the canard-wing interaction is o particular interest. The presence o a canard in close proximity to the wing results in a highly coupled canard-wing lowield interactions which includes downwash/upwash eects, vortex-vortex interactions and vortex-surace interactions. The use o canards or improved perormance has been supported by numerous experimental investigations as well as some recent computational studies. An early experimental study by Behrbohm [1] indicated the potential use o closed-coupled canard conigurations or improved aerodynamic characteristics based on the canard-wing interaction. It has been ound that the value o maximum lit coeicient and the corresponding angle o attack can be increased considerably by adding a delta canard to a delta wing. Gloss and McKinney [2], and Gloss [3, 4] provided insight into the eects o canard geometry and position on the aerodynamic loading o a typical canard-wing-body combination. An extensive experimental study was conducted by Hummel and Oelker [5, 6], which concentrated on the canard and Received by the editors April 11, 212; Accepted October 15, 213. Corresponding author

2 134 S. Samimi et al. wing vortex systems. They provided details into the mechanisms o the vortices interaction. They also traced vortex trajectories and determined the eect o the canard vortices on the surace pressure distribution over the wing. The experimental study by Howard and Kersh [7] provided detailed inormation on the low structure o delected canard geometries in the low subsonic regime and has shown encouraging results towards the optimization o such conigurations. Up to 199, the experimental surveys were generally concentrated on the canard-wing conigurations without taking the uselage eects into account. In 1993, Howard [8] tested a canard- wing model including uselage. A tertiary vortex was observed at the juncture o canard and uselage that had an impact on the resulting lowield and was not evident in the studies o wing-canard combinations in the absence o body. Zhiyong [9] studied the eect o position and platorm o canard-wing conigurations on the burst process o the leading edge vortices o a double delta wing as well as the aerodynamic characteristics o a ighter coniguration equipped with a double delta wing. Based on these indings, he proposed an optimum ighter coniguration with canard and a double delta wing Hayashibara et al. [1] during an experimental study in a water tunnel investigated the eect o a canard-on delta wing vortices o a high canard-wing coniguration. They exploited the die low visualization technique to observe the vortex breakdown location and its variations during dynamiitchup and pitch-down motions with varying pitch rates. They ound that compared to canard-o coniguration, there is a delay in vortex breakdown due to the presence o the canard and the dynamic pitch motion. The most avorable delay was obtained when the canard was located very closed to the main delta wing and the model was pitched up at a ast rate or pitched down at a slow rate. Guy et al. [11, 12] conducted an experimental investigation to study the eects o canard shape on the aerodynamic characteristics and perormance o a generic canard-wing-body coniguration. They examined the eects o canard aspect ratio, sweep angle and taper ratio on the aerodynamic loads o the coniguration in subsonic low. They proposed a new method to evaluate the canard eiciency by measuring moment-to-drag ratio Bergmann and Hummel [13] examined the body-wing-canard conigurations in a symmetrical low. Their results indicate that the eects o canard vortex on the low over the wing are considerable or large delections and or a low canard position, i.e. the canard surace is much lower than that o the wing. However, at very low canard positions, this avorable intererence eect vanishes. The vortex breakdown on the canard deteriorates the vortical low at all angles o attack and leads to a considerable loss o lit. Close-coupled canard conigurations have also been the subject o computational studies or a long time. Numerical computations o low ields around such conigurations show encouraging agreement with the available experimental data. Tu [14, 15] studied transonic low over a canard wing body coniguration by means o thin-layer Navier Stokes equations. He calculated the strong eect o the canard vortex on the strength, reattachment, and separation o the wing vortex. He urther calculated the eect o the canard-on the surace pressure distribution. Similar solutions were perormed by Ekaterinaris [16] or the coniguration studied by Hummel et al. [5, 6] at low subsonic speeds. He limited his analysis to laminar low computations or 2 degrees incidence only, but conirmed the delay o vortex breakdown resulting rom the canard and obtained good agreement with Hummel s data. Tuncer and Platzer [17] investigated the subsonic low ield over a close-coupled delta canard-wingbody coniguration at high angles o attack using a Navier-Stokes solver. They presented their results in terms o particle traces, surace streamlines and leeward-side surace pressure distributions or both IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

3 Canard-wing interactions in subsonic low 135 canard-on and canard-o conigurations. They ound that the presence o the canard delays the wing vortex breakdown to positions at o the wing trailing edge. Recently, the optimization algorithms were employed to optimize the canard shape and position by either numerical or analytical methods. These optimizations were, or instance, to reduce the sonic boom reduction and improve the lit to drag ratio or supersonic transports [18] or to achieve a desired trim light control orce [19], etc. Nearly all studies undertaken so ar were concentrated on the canard eects on the orces and moments o the aircrat or the canard signature on the low ield over the wing. Though valuable inormation has already been obtained on the eects o canard-on the low ield over the wing, to the authors' knowledge, the upstream inluence o wing on the canard as well as the power spectrum analysis o canard and wing vortices have seldom been studied. In the present research, eects o canard-on the wing low ield and wing on the canard were investigated in a canard-wing-body coniguration. The results include the surace pressure distribution on wing and canard as well as the wing alone pressure data as a benchmark to study the canard-wing low interactions. The requency content o instantaneous pressure luctuations on both the wing and the canard were estimated using the power spectral density (PSD) unction o the unsteady component o the dierential pressure coeicient. The dierential pressure time histories rom each test condition were converted into the requency domain using Discrete Fourier Transorm (DFT) techniques. The average PSD unctions were obtained by averaging the Discreet Fourier transorms. The dominant requencies o the instantaneous pressure were identiied rom the power spectral density plots. The results can be thought o as a dierent view point to the vortex interaction phenomenon. These indings can be extensively used in all canard-wing vehicles at moderate to high angles o attack in a subsonic low. 2. MODEL AND EXPERIMENTAL APPARATUS The present experiments have been carried out in a closed circuit, 8 8 cm subsonic wind tunnel. The maximum attainable speed in the test section is 1 m/sec and the Reynolds number varies between and per meter. Turbulence intensity in the test section has been measured to be less than.1%. This investigation has been perormed on a coplanar close-coupled canard-wing-body coniguration. Figure 1 shows the model installed in the test section. Both the wing and the canard have delta planorms o aspect ratio 1.17 and 1.15 respectively, and a corresponding leading-edge sweep o 6. They were made o aluminum alloy and attached to a hal-body uselage. 64 and 27 pressure tabs were careully drilled on the upper surace o the wing and the canard respectively. Fig. 2 shows the pressure tabs position on both the wing and the canard. Each tab was connected to a sensitive pressure transducer to measure the surace pressure distribution on both planorms. The experiments were conducted at a nearly constant air speed o 6 m/sec corresponding to a Reynolds number o based on the wing root chord. The model angle o attack was varied rom 1 to 3. All data were acquired by an AT-MIO-64E data acquisition board capable o scanning 64 channels at a rate o 5 KHz. Total errors encountered in the pressure measurements including the accuracy o the electronic devices such as transducers and acquisition board as well as the errors imparted to the data due to low angularity and blockage eects were estimated by analytical approaches [2, 21]. Both the single sample precision and the bias uncertainty in the pressure measurement were also taken into account. Based on the method mentioned in the above reerences, the overall uncertainty or the presented data is less than ± 3.%. October213 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2

4 136 S. Samimi et al. Figure 3 shows the result o a typical data uncertainty analysis on wing and canard surace pressure measurements. 3. RESULTS AND DISCUSSION The experiments consisted o real time pressure measurements on both canard and wing in the canardwing coniguration. A canard-o coniguration was also examined as well or comparison. Since both the wing and the canard have the same sweep angles, the dierences in the corresponding lowields are believed to be due to up and down stream inluences o these liting suraces on each other as well as the uselage lowield. A power spectrum analysis was also conducted on the surace pressure values, determining the vortex behavior on wing and canard. Figure 4 shows the results o surace pressure distribution at dierent angles o attack or both the canard-on and canard-o conigurations at several chordwise stations. The leading-edge vortex signature can be detected rom the suction peaks on both conigurations. An interesting point observed in Fig. 4 is the location o the vortex core on the wing. For wing in presence o canard, i.e. canard-on case, the wing vortex is shited towards the leading edge, while or the canard-o case the core was closer to the wing root. At small to moderate angles o attack, the absolute value o pressure on the wing or canard-o coniguration is slightly lower than that or the corresponding canard-on case or x/c s near the wing trailing edge. In other words, or the canard-on coniguration, the suction peaks on the wing surace pressure at ront regions are higher than those or the canard-o cases, while at the rear near the wing trailing edge, the value o the suction peak or the canard-on coniguration has been reduced. So it can be inerred that the domain o avorable inluence o the canard is mostly restricted to the ront and middle parts o the wing at moderate to high angles o attack. From Fig. 4, or the canard-o coniguration at 2 degree angle o attack, the vortex breakdown seems to occur at the rear part o the wing, Fig. 4a. This is in accordance with the existing experimental data or a simple 6 degree swept wing [22]. At α=3, the vortex structure over the wing surace in canard-o case has nearly been destroyed or all sections shown in Fig. 4, while or the canard-on coniguration the wing vortex is still active throughout the wing and the suction peak can be observed in the pressure distribution at this angle o attack. On the other hand, canard induces behind its trailing edge a downwash ield within its span and an upwash ield outside its span. The downwash ield reduces the eective angle o attack in the inner portion o the wing considerably, and this leads to a suppression o low separation there. The upwash ield increases the eective angle o attack in the outer portions o the wing, and this supports low separation there. This mechanism postpones ormation and breakdown o the wing vortex or canard-on coniguration. Because o the nonuniorm distribution o the eective angle o attack along the leading edge o the wing, the wing vortex is ed with vorticity in a dierent manner than is known rom the canard-o conigurations. Generally speaking, the wing in presence o canard, works at a lower eective angle o attack than an isolated wing. The canard surace pressure distributions are shown at our longitudinal positions in Fig. 5 or various angles o attack. The pressure distribution on the canard is very similar to that o the wing or the canard-o coniguration shown in Fig. 4, except or the trailing-edge region, where the absolute values o surace pressure on the canard seem to be increased compared to the corresponding locations on the wing alone. This is especially the case or high angles o attack, where the burst low is dominated on the rear part o the wing with substantially lower pressures than those at moderate angles o attack. However, on the rear part o canard at high angles o attack, the amount o suction is obviously higher than that o the IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

5 Canard-wing interactions in subsonic low 137 wing having the same sweep angle. This is believed to be due to the avorable acceleration eect rom the wing up to 25 degrees angle o attack, which is due to wing upwash eect, Figs. 5c and d. The spectral content o the dierential pressure luctuations at an angle o attack o 15 degrees at our chordwise positions is illustrated in Fig. 6. For all positions examined here, the energy content o the low ield is mainly concentrated in a relatively narrow requency band in the range o 7 to 1 Hz with the dominant requency o about 8.5 Hz. This requency is believed to be associated with the wing leading edge vortex. The accumulated energy in this limited band may be an indication o a periodic or quasi periodic luctuation which is due to the swirling vortex pattern. This peak in the pressure power spectrum occurs at about the same requency over the entire surace o the wing while its amplitude is clearly dierent or each position. The power spectrum at x/c =.313 shows a smaller peak compared to the two next chordwise locations. It seems that the vortex structure at this location on the wing surace has been deteriorated by the canard low and thereore, the small peak in the power spectrum at x/c =.313 is the canard vortex signature on the wing, Fig. 6a. At x/c=.563 and.688 the peak value at the dominant requency shows a remarkable increase, Figs. 6b and 6c. Strong peaks and high oscillations are expected rom the points on the wing located either on the way o the wing leading edge vortex or the extension o the canard vortical low. At x/c=.563, maximum value o the power spectrum occurs at point 21, which means that at this angle o attack and chordwise position, the vortex core is very close to this point. At x/c=.875, Fig. 6d, the dominant requency is the same as that or the other chordwise locations, while the peak value at this requency, which is an indication o the vortex energy level, is clearly lower than that measured at other positions. The leading edge vortex near the trailing edge at this angle o attack lits o rom the surace and the pressure tabs located on the wing surace receive less inluence rom it. Further, at low to moderate angles o attack, the domain o the avorable inluence o canard is mostly restricted to the ront and middle portions o the wing. This has been shown to attenuate the wing vortex strength near the trailing edge [22]. In addition to the dominant peak corresponding to the wing vortex natural requency, another characteristic requency, lower than the ormer, with smaller amplitude is observed in the power spectrum. The large eddy ormation in the wake region o canard may be the reason or this low requency excitation. A ew high requency random luctuations are also observed, which are probably caused by the strong interaction o the wing and the canard vortices. These high requency excitations in the power spectrum can also be due to the energetic vortices shed rom the nose and body, which have been shown to improve the lowield over the wing at moderate to high angles o attack [22]. It should be noted that some o the random luctuations are also caused by the tunnel noise as well as the ree stream turbulence. However, according to hot wire measurements, the turbulence level in this tunnel was less than.1%. For urther insight, the power spectra or some neighboring points at two middle chordwise sections x/c=.563 and x/c=.688 on the wing at dierent angles o attack are shown in Fig. 7. Evidently, the amplitude o the dominant requency changes with angle o attack due to changes in vortex strength and position. As noted earlier, or point 21 the maximum amplitude occurs at α=15 and decreases with increasing the angle o attack, Fig. 7a. Spectral content o pressure luctuations at point 22, Fig. 7b, shows that or both angles o attack o 2 and 25 degrees the amplitudes o the dominant requency peaks are signiicantly larger than those or point 21 at the same angles o attack. This suggests that the position o vortex core moves rom point 21 to 22, i.e. toward the body, as increasing the angle o attack. The same argument seems to be true or points 3 and 31 at x/c=.688, Fig. 7c and 7d. For all angles o attack examined here, the amplitudes o the dominant requency mode or point 31 are larger than those o point 3 and thereore the vortex core can be deduced to be closer to point 31 near the body. Apart rom the vortex movement towards the body as increasing angle o attack, the vortex lit-o rom the body may October213 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2

6 138 S. Samimi et al. also be responsible or decreasing the dominant requency peak with angle o attack. Furthermore, or all points at 2 and 25 degrees angle o attack, the dominant requency decreases. This gradual decrease o the characteristic requency is likely a consequence o canard and wing vortex merging which occurs at moderate to high angles o attack. A dramatic change occurs in the spectral density at α=3 and the dominant requency increases to about 9.5 Hz due to the wing leading edge vortex breakdown. This value may correspond to the requency o the burst vortex. The dominant peak at this angle o attack results rom the strong interaction o the unsteady structure o vortex breakdown with the wing surace. As the vortex breakdown occurs, the region o high pressure scatters and propagates over the wing and imposes a certain degree o random luctuations to the surace pressure ield. In particular, the low-requency region in the pressure power spectrum begins to rise rapidly due to vortex breakdown at all points on the wing. The pressure power spectra on the canard surace are shown in Fig. 8 or two chordwise locations at 15 degrees angle o attack. As can be seen, the power spectra or the canard are similar to those or the wing. However, compared to the wing results, the amplitude o the dominant requency mode is considerably smaller, especially at x/c=.615, Fig. 8a, compared to x/c=.563, Fig. 6b, on the wing. Further, the dominant requency on the canard pressure power spectrum, or all cases, is larger than that or the wing. Since the sweep angles or both the wing and the canard are the same, i.e. 6, the dierences between the pressure spectra o these two suraces are associated with the canard wake and the vortex eects on the wing. Comparing Fig. 8a with Figs. 6b and 6c at nearly the same chordwise positions, the increased number o the oscillatory modes in the wing pressure power spectrum due to presence o the canard is obvious. It also seems that the canard decreases the requency o vortex ormation over the wing. Comparing the power spectra at x/c=.615, Fig. 8a and x/c=.769, Fig. 8b, at the latter, an increase is observed in the power spectrum intensity to a value about twice as large as that at the ormer station while the dominant requency is nearly constant or both. To achieve better insight, the variation o power spectrum or neighboring points at mentioned chordwise positions on canard are presented in Fig. 9 at dierent angles o attack. The results illustrate that with increasing angle o attack, the spectrum intensity is ampliied due to an increase in the strength o the leading edge vortex, and requency bandwidth decreases. Furthermore, the vortex trajectory shits inboard as increasing the angle o attack. At α=2, pressure luctuations begin to rise rapidly with multiple peaks. This is a clear indication o vortex burst phenomenon. The pressure luctuations at this angle o attack result rom the strong interaction o the unsteady structure o vortex breakdown with the canard surace. With urther increase in angle o attack a characteristic increase in surace pressure luctuations is observed due to vortex bursting, especially when the burst location moves toward the apex. Figures 1 through 13 show the downstream inluence o canard-on the wing as well as the upstream inluence o wing on the canard at our chordwise sections. Since both the wing and the canard have the same sweep angles, the low patterns on either o them can be compared to that o another. According to Fig. 1a at α=1, the wing pressure on the suction side, which is an indication o the vortex strength, or the wing alone is higher than either the wing or canard in the canard-wing coniguration. This implies that the presence o canard decreases the vortex strength on the wing and, on the other hand, the wing does the same on the canard. However, in canard-wing coniguration the drop in vortex strength or wing downstream o canard is higher than that or canard upstream o wing. IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

7 Canard-wing interactions in subsonic low 139 According to Figs. 1c and 1d at high angles o attack, the canard-on coniguration show a higher perormance than the canard-o case. As beore, the avorable eect o wing on the canard is stronger than that o canard-on the wing with equal sweep angles. Thus, in canard-wing interaction at low angles o attack, the lowield on the wing at the ront sections is more deteriorated than the corresponding sections on the canard. At high angles o attack, the isolated wing at canard-o coniguration is shown to have a lower perormance than either o the wing and the canard in canard-on coniguration. However, the upstream inluence o the wing on the canard is still more avorable than the downstream inluence o the canard-on the wing. Similar behavior can be observed in Fig. 11 at x/c=.563. At all angles o attack, the canard upstream o the wing experiences a stronger suction than the wing downstream o canard, both having the same sweep angles. Compared with the isolated wing, Fig. 11 shows that the canard perormance due to presence o wing is higher than that o the wing in presence o canard. This clearly indicates the avorable eect o wing on the canard and the adverse impact o canard-on the wing at the ront regions o both suraces. Note that at this middle chordwise station, the wing alone (canard-o) coniguration has a better perormance than the wing in presence o canard or a wide range o angle o attack. A noteworthy problem in Fig. 11 is the vortex position. The wing vortex downstream o the canard is shited outboard towards the wing tip, while the canard vortex upstream o the wing is observed to be moved inboard towards the root compared to the wing alone coniguration. This phenomenon is believed to be due to the wing upwash eect on the canard and that o canard downwash on the wing. According to the experimental investigations or a 6 degree swept wing, the vortex burst point reaches the trailing edge at an angle o attack o about 16 degrees [23]. For higher angles o attack, i.e. 2, 25 and 3 degrees, shown in Figs. 11b, 11c and 11d, the burst point occurs on the wing and canard suraces moving towards the leading edge as the angle o attack increases. From Fig. 11d, it seems that the vortex burst position at α=3 has reached about x/c=.563 or isolated wing. At this angle o attack, a vortex is seen on the wing in presence o canard which has not been observed on the wing alone. This vortex may be induced by the canard vortical low, which ormed a suction region on the wing and the burst vortex has been retrieved. For the two rear sections x/c=.688 and.875 shown in Figs. 12 and 13, the canard upstream o the wing still shows a better aerodynamic behavior than the wing alone coniguration. In these two sections at moderate to high angles o attack, the maximum value or the suction on the wing in presence o canard is a little higher than that or wing alone with a more concentrated vortical low region. Further, in all o these igures, the canard vortex was pushed towards the root and the wing vortex has been displaced towards the tip in comparison to the vortex position or wing alone coniguration. This phenomenon, as stated earlier, is due to the wing upwash eects on the canard as well as the canard downwash eects on the wing and is observed at both low and high angles o attack. 4. CONCLUSION An in-depth study has been undertaken on a coplanar wing-canard coniguration in subsonic low to study the impact o canard-on the wing and that o the wing on the canard in a relatively wide angle o attack range. Both the wing and the canard in these experiments had equal sweep angles o 6 degrees. The results show that canard postpones the vortex ormation, growth and burst on the wing to some higher angles o attack compared to the isolated wing coniguration. This avorable eect o canard-on the wing is restricted to the ront and middle portions o the wing at low to moderate angles o attack. On the other hand, the wing was observed to induce a avorable lowield on the canard at all angles o attack, especially at the rear region o the canard. This implies that the upstream inluence o wing on canard ampliies the canard vortex strength and pushes it towards the root, while the downstream inluence o canard-on the wing displaces the wing vortex towards the tip and at low angles o attack, decreases its October213 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2

8 14 S. Samimi et al. strength at the ront parts o the wing. However, at high angles o attack, the canard is shown to have a avorable impact on the wing at the ront parts. The pressure power spectrum analysis on both the canard and the wing shows that the dominant requency o the leading edge vortex on the wing in presence o canard is smaller than that on the canard having the same sweep angle in presence o wing. It can be inerred that the downstream inluence o canard, apart rom its dierent eect on the wing at ront and rear regions, has decreased the wing vortex energy level, showing the diusive character o the downwash eects along with the dissipative eects o canard wake on the wing or both small and large angles o attack. Fig. 1. The model installed in the test section (a) Canard (b) Wing Fig. 2. The positions o the pressure tabs Fig. 3. Typical data uncertainty analysis IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

9 Canard-wing interactions in subsonic low Canrd-o, x/c=.563 =1 o.6..4 Canrd-on, x/c=.563 =1 o (a) Canard-o, x/c=.563 Canrd-o, x/c=.688 =1 o (b) Canard-on, x/c=.563 Canrd-on, x/c=.688 =1 o (c) Canard-o, x/c=.688 Canrd-o, x/c=.875 =1 o (d) Canard-on, x/c=.688 Canrd-on, x/c=.875 =1 o (e) Canard-o, x/c=.875 () Canard-on, x/c=.875 Fig. 4. Canard eects on spanwise pressure distribution on the wing x/c=.462 =1 o x/c=.615 =1 o x/c=.769 =1 o (a) x/c= x/c=.923 (b) x/c=.615 =1 o (c) x/c=.769 (d) x/c=.923 Fig. 5. Canard surace pressure distribution October213 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2

10 142 S. Samimi et al Point 4 Point 5 Point 6 w =15 o,x/c= Point 2 Point 21 Point 22 w =15 o, x/c= (a) x/c=.313 Point 3 Point 31 Point 32 w =15 o,x/c= (b) x/c=.563 Point 51 Point 52 Point 53 w =15 o,x/c=.875 (c) x/c=.688 (d) x/c=.875 Fig. 6. Wing pressure power spectrum, α= point #21, x/c= point #22, x/c= (a) x/c=.563, point #21 (b) x/c=.563, point #22 point #3, x/c= point #31, x/c=.688 (c) x/c=.688, point #3 (d) x/c=.688, point #31 Fig. 7. Wing Pressure power spectrum or neighboring points IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

11 Canard-wing interactions in subsonic low Point 12 Point 13 Point 14 w =15 o,x/c= Point 17 Point 18 Point 19 w =15 o, x/c=.769 (a) x/c=.615 (b) x/c=.769 Fig. 8. Canard pressure power spectrum, α= point #12, x/c= point #13, x/c= (a) x/c=.615, point #12 (b) x/c=.615, point #13 point #14, x/c= point #17, x/c= (c) x/c=.615, point #14 (d) x/c=.769, point #17 point #18, x/c= point #19, x/c=.769 (e) x/c=.769, point #18 () x/c=.769, point #19 Fig. 9. Canard pressure power spectrum or neighboring points October213 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2

12 144 S. Samimi et al (a) α= (b) α= (c) α=25 (d) α=3 Fig. 1. Spanwise pressure distribution at x/c= (a) α= (b) α= (c) α=25 (d) α=3 Fig. 11. Spanwise pressure distribution at x/c=.563 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

13 Canard-wing interactions in subsonic low (a) α= (b) α= (c) α=25 (d) α=3 Fig. 12. Spanwise pressure distribution at x/c= (a) α= (b) α=2 October (c) α= (d) α=3 Fig. 13. Spanwise pressure distribution at x/c=.875 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2

14 146 S. Samimi et al. REFERENCES 1. Behrbohm, H. (1965). Basic Low speed aerodynamics o the short-coupled canard coniguration o small aspect ratio. SAAB Aircrat Co. TN-6, Linkoping, Sweden. 2. Gloss, B. B. & McKinney, L. W. (1973). Canard-wing lit intererence related to maneuvering aircrat at subsonic speeds. NASA TM X Gloss, B. B. (1974). The eect o canard leading-edge sweep and dihedral angle on the longitudinal and lateral aerodynamic characteristics o a close-coupled canard-wing coniguration. NASA TN D Gloss, B. B. (174). Eect o canard location and size on canard-wing intererence and aerodynamic-center shit related to maneuvering aircrat at transonic speeds. NASA TN D Oelker, H. Chr. & Hummel, D. (1989). Investigations on the vorticity sheets o a close-coupled delta-canard coniguration. ICAS Proceedings, Vol. 1, 1988, pp ; see also Journal o Aircrat, Vol. 26, No. 7, pp Hummel, D. & Oelker, H. Chr. (1989). Eects o canard position on the aerodynamic characteristics o a closecoupled canard coniguration at low speed. AGARD-CP65, pp. 7-78; see also Zeitschrit ur Flugwissenschaten und Weltraumorschung, Vol. 15, No. 2, pp Howard, R. M. & Kersh, J. M. Jr. (1991). Eect o canard delection on enhanced lit or a close-coupled-canard coniguration. AIAA Paper CP. 8. Howard. R. M. & O Leary. J. F. (1994). Flow ield study o a close-coupled canard coniguration. Journal o Aircrat, Vol. 31, No Zhiyong, L. (1997). A study on low patterns and aerodynamic characteristics or canard double delta wing coniguration. AIAA Paper Hayashibara, S., Myose1, R. Y. & Miller, L. S. (1997). The eect o a 7 swept canard-on the leading edge vortices o a 7 swept delta wing during dynamiitching. AIAA Paper Guy, Y., Morrow, J. A. & McLaughlm, T. E. (1999). The eects o canard shape on the aerodynamic characteristics o a generic missile coniguration. AIAA Paper Guy, Y., McLaughlm, T. E. & Morrow, J. A. (2). Eects o canard shape on the center o pressure o a generic missile coniguration. AIAA Paper Bergmann. A. & Hummel, D. (21). Aerodynamic eects o canard position on a wing body coniguration in symmetrical low. AIAA Paper Tu, E. L. (1992). Navier-stokes simulation o a close-coupled canard-wing-body coniguration. Journal o Aircrat, Vol. 29, No. 5, pp Tu, E. L. (1994). Eect o canard delection on close-coupled canard-wing-body aerodynamics. Journal o Aircrat, Vol. 31, No. 1, pp Ekaterinaris, J. A. (1995). Analysis o low ields over missile conigurations at subsonic speeds. Journal o Spacecrat and Rockets, Vol. 32, No. 3, pp Tuncer, I. H. & Platzer, M. F. (1996). A computational study o a close-coupled delta canard-wing-body coniguration. AIAA Paper 9644-CP. 18. Yoshimoto, M. & Uchiyama, N. (23). Optimization o canard surace positioning o supersonic business jet or low boom and low drag design. AIAA Paper Joshi, A. & Suryanarayan, S. (25). Optimal location and size o canards or aeroelastic actuation in aerospace vehicles. AIAA Paper Rae, H. W., Jr. & Pope, A. (1984). Low-speed wind tunnel testing, John Wiley & Sons, Inc. IJST, Transactions o Mechanical Engineering, Volume 37, Number M2 October 213

15 Canard-wing interactions in subsonic low Thomas, G. B., Roy, D. M. & John, H. L. V. (1993). Mechanical measurements. Addison-Wesley Publishing Company, Soltani, M. R., Askari, F., Davari, A. R. & Nayebzade, A. (21). Eects o canard position on the wing surace pressure. International Journal o Science and Technology, Scientia Iranica, Transaction B: Mechanical Engineering, Vol. 17, No. 2, pp Malcolm, G. N. (1981). Impact o high alpha aerodynamics on dynamic stability parameters o aircrat and missiles. AGARD Lecture Series No October213 IJST, Transactions o Mechanical Engineering, Volume 37, Number M2