Wind Tunnel Testing Guidance. Arjan Voogt

Transcription

1 Wind Tunnel Testing Guidance Arjan Voogt

2 WIND TUNNEL TESTING Proven method for airplanes, city planning, car design competitive cycling, rockets trajectories and skiing

3 BUT NOT ACCEPTED BY USCG IN STABILITY EVALUATIONS Stability of Floating Offshore Installations is regulated by the Code of Federal Regulations (46CFR) and enforced by the US Coast Guard (USCG). 46CFR includes a numerical method to determine wind forces and moments for stability calculation, but provides no guidance on alternative methods such as wind tunnel model testing.

4 BACKGROUND The numerical model often results in apparently more conservative stability, because it is based on a building block approach for drag coefficients on different elements without considering the effect of shielding. Uncertainty in test results from the wind tunnels. Well established institutes can measure up to 30% different overturning loads for similar platforms A number of FOI designers and operators have expressed the need to make wind tunnel tests a USCG accepted practice; this will improve the certainty on the results and the effectiveness of the facilities. The USCG is also interested in such a development but will only accept model testing if carried out following scientifically proven acceptance criteria and standard procedures.

5 SNAME T&R BULLETIN 5-4 There is no adequate industry guidance for model testing of large and more complex FOI s, other than an outdated SNAME T&R Bulletin 5-4 Guidance on Wind Tunnel Testing on MODUs Systematic benchmarking of wind tunnel results across different facilities to understand the disparity in results doesn t exist.

6 SNAME OC-1 WORKING GROUP Tasked with preparation of update to SNAME T&R Bulletin 5-4. Guidance will be revised to provide a framework for Agencies and Industry acceptance of using wind tunnel testing for the design of Floating Offshore Installations. Standardization needed to reduce uncertainty in wind tunnel tests results

7 REASON 1: PHYSICAL LIMITATIONS OF WIND TUNNELS Scale Blockage, model size to wind tunnel size ratio Boundary layer profiles, errors and consequences. API, ABS, DNV Boundary layer profile creation differences / types and effects Turbulence Intensity effects

8 REASON 2: AMOUNT OF DETAILS IN THE MODEL Crane simulation/detail effects. Derrick simulation/detail effects. Helideck simulation/detail effects. Model equipment detail effects. Underdeck detail effects. Model surface roughness effects.

9 REASON 3: MEASUREMENT EQUIPMENT AND SETUP Difference between External Balance, Internal Balance or other balance systems Floor plate gaps effects Leakage effects

10 DEEPSTAR PROJECT PROPOSED Proposal: The project aims to standardize wind tunnel testing procedures via benchmark testing of a representative Floating Offshore Installation in several wind tunnel testing facilities. Vision of Success/Goals: Criteria for Acceptance of Facilities, Standardized Testing Procedures and vetting of wind tunnel test results acceptable to Agencies and Industry Deliverables: Deliverables: Wind tunnel model test reports from selected Wind Tunnel Testing Facilities Comparison and reconciliation report on test results from different facilities Updated version of SNAME T&R 5-4 approved by the SNAME OC-1 panel

11 DEEPSTAR PROJECT SCOPE OF WORK Benchmarking tests of a representative floating offshore installation. Perform benchmarking tests in three wind tunnel test facilities Identify uncertainty level due to modeling choices, measurement techniques and tunnel characteristics. Resolution and reconciliation of differences in test results with in-kind CFD SNAME T&R 5-4 revised based on findings in the wind tunnel testing results.

12 MARIN WINDLOAD JIP Currently in its start up phase Focusing on effects of boundary layer effects, vessels coming into port, & FPSO offloading Potential arrangements to be made for data exchange between DeepStar and the wind tunnels participating in the Marin JIP.

13 BACKGROUND WIND LOAD JIP More complex Bigger ships Close proximity Operations requires thorough preparations, often with simulation models. Wind and wind shielding plays important role

14 OBJECTIVES Define a standard for the modeling of atmospheric boundary layer wind profiles and wind flow around structures in wind tunnels and in CFD models. Provide carefully checked wind load coefficients for a typical FPSO, a semisubmersible, a cruise boat and a container ship. Demonstrate nowadays CFD capabilities for wind load predictions for complex offshore and ship structures Perform a benchmark study Write guidelines for wind tunnel tests and CFD calculations for wind load prediction for complex offshore and ship structures.

15 PARTNERS WIND LOAD JIP MARIN TU/e, Eindhoven University of Technology The Foundation German-Dutch Wind Tunnels (DNW) BMT Fluid Mechanics Ltd.

16 WORK PACKAGES WIND LOAD JIP 1. Definition of 3D wind fields in wind tunnels and CFD calculations 2. Wind tunnel measurements and CFD computation of wind loads on complex offshore and ship structures 3. Benchmark study for alternative wind tunnels and CFD providers 4. Dissemination of results and writing of guidelines More info on this: NEXT TUESDAY OPEN MEETING AT HOTEL SORELLA SIGN UP AT

17 SYNERGY JIP AND DEEPSTAR PROPOSAL Wind velocities CFD and wind tunnel measurements on Benchmark Guidelines WindLoad JIP Open area vertical velocity profiles Complex Offshore constructions and ship structures Optional for alternative tunnels Work package BMT, Project summary and advice DEEPSTAR 3D wind fields, shielding, focusing Floating Offshore Installations (stability of semi s) Main goal of study with 3 levels of comparison to develop guidelines SNAME paid study Industry acceptance, agency approval

18 CONCLUSIONS Update to wind tunnel test guidance needed for Stability check on Floating Offshore Installations acceptable to agencies and industry More complex operations on larger vessels (offshore offloading, larger ships entering existing ports) Initiatives underway: Possible Deepstar proposal award in November (2 year project duration) MARIN WindLoad JIP will run from 2014 to Projects are complimentary and further cooperation will be discussed to maximize leverage.

19 QUESTIONS? For questions on wind load JIP: Open meeting October 15 th, 1.30pm 5pm Hotel Sorella Sign up at