Stability and Hydrostatic analysis SESAM User Course in Stability and Hydrostatic Analysis HydroD Workshop: Perform the analysis in HydroD The text in this workshop describes the necessary steps to do stability and hydrostatic analysis of a barge with a jacket on top. The barge has 8 tanks which can be filled independently in this workshop you are asked to do various tank fillings to see the effect on both equilibrium position and the computed GZ-curves. The panel model, structure model (used to describe the tanks) and the mass model has been created in GeniE. The total mass of the structure (mass model) is 9011 tonnes. The file describing the model is called HydroD_Stab_Ex1_T1.FEM. If you have used the default installation, this file is located C:\Program Files (x86)\dnvgl\hydrod V4.*- **\Examples\Barge In x-direction the max and min x-values are -45.72m and 45.72m In addition to the text input, there is also a journal file Barge_Jacket_Stability_in.js that you can read into HydroD to rapidly reproduce the workshop. Please make sure that the journal file and the FEM file has been copied to the project directory set up by HydroD. This workshop should be viewed on-line or on colour print out to best see the property colour coding. X min = -45.72m X max = 45.72m The model created in GeniE 1
Part 0 - General Tank 2 Tank 4 The internal tanks as defined in GeniE Tank 6 Tank 8 Tank 1 Tank 3 Important notes: The barge has eight tanks as shown above. The tank filling is done in HydroD by the user (or from using the feature for tank balancing). The wetted surface to describe the panel model has also been defined in GeniE. Any of the structures are fictitious model and the sea fastening arrangement has been simplified from a conventional arrangement the main purpose of this workshop is not structure but hydrostatics The units are meter and kg. All pictures created by GeniE and HydroD are shown using white background (View Options General Paper Background). This may be different from your background. Tank 5 Tank 7 All tanks have the same volume Vtank = 832.895 m 3 Model origin at (0m, 0m, 0m) as shown above 2
Part 0 - General The workshop is split as follows (start modelling from Part 1 and onwards) Part 0 General introduction to the workshop and start HydroD Pages 1-4 Part 1 using the stability wizard to make model and do initial analysis For new users the wizards will guide you through all necessary steps to make a model fit for stability and hydrostatic computations. For more experienced users, similar modelling and analysis are done by using pull-down menus, tool-buttons or from the context sensitive menu in the browser. Pages 5-35 Part 2 Create a new loading condition with changed compartment filling How to copy a loading condition, change the compartment fillings and find a new equilibrium position Pages 36-38 Part 3 Create damaged loading condition This part uses the previously generated loading condition as the starting point of a damaged loading condition Pages 39-41 Part 4 Execute multiple stability analysis Generate multiple hydrostatic analysis and execute them. View the results. Pages 42-50 Part 5 Make a clean journal file Save the input files (journal files) for later use Pages 51 3
Part 0 - General Start HydroD and make a new workspace You start HydroD from Desktop From Start menu You make a new workspace (or a project) from File New Workspace and give it a name For this workspace we use units meters and Newton 4
Activate the wizard You activate the wizard from the tool-button You need to specify what type of model you will be working with, this workshop assumes a pure panel model. 5
You may also change the default settings (i.e. filter out steps in the wizards) by clicking on Settings. In this tutorial we will not do an allowable VCG analysis, so untick this. 6
Step 1 in the wizard Create a location Specify name ( Doggerbank in this case), water density, kinematic visosity and water depth. Remember also to add details for the air Step 2 in the wizard Create a hydro model Specify a name and decide fixed or floating structure. Baseline, AP and FP positions are only relevant for Wasim analysis, so you don t need to change these. 7
Step 3 in the wizard Create a panel model The panel model specifies the outer wetted surface. The wetted surface is being used to calculate the floater buoyancy. The panel model has been made in GeniE To import, locate the file HydroD_Stab_Ex1_T1.FEM stored under C:\Program Files (x86)\dnvgl\hydrod V4.*-**\UserExamples\Barge\inp. The path name assumes you have installed the program HydroD using default values when installing There are no symmetry planes in this model and the coordinate system of the imported model coincides with the coordinate system of the hydro model 8
Step 3 in the wizard Cont d The panel model is now shown in your display window 9
Step 4 in the wizard Create load cross sections (Press next) Cross-sections must be defined where you want HydroD to compute still water forces and moments The wizard will guide you to define several cross sections one by one This workshop will instead use the Multiple load crossections option. This is reached by right clicking the LoadCrossections folder and choosing Multiple load cross sections. Define cross sections as shown below 10
Step 5 in the wizard Create the structure model. The tank definitions are now imported Similar to the panel model, the structure model has been created in GeniE. To import, locate the file HydroD_Stab_Ex1_T1.FEM stored under C:\Program Files (x86)\dnvgl\hydrod V4.*-**\UserExamples\Barge\inp. The panel model, the structure model and the crossections are are now being shown in the graphical window 11
Step 5 in the wizard Cont d Hint: You may switch your focus view by using the Modelling Draw Style feature Below is shown how to look at the structure model only and also how to change colours of the beams to dark blue Remove the panel model and LoadCrossSections from view 12
Step 5 in the wizard Cont d Hint: You may switch your focus view by using the Modelling Draw Style feature The beams are now shown with dark blue colour. Plates are shown with grey colour 13
Step 6 in the wizard Create permeability factors Permeability factors are used to specify whether a tank (or compartment) is filled with solid content. A permeability factor of e.g. 0.9 indicates that the compartment can be filled with 90% of the total compartment volume. In this model, a permeability factor of 1.0 is used. This means that all tanks are clean inside and can be filled to 100% of tank volumes. Click OK to proceed to next step. 14
Step 7 in the wizard Create compartments The compartments are automatically found from the structure model. The compartments will receive properties for permeability and deck tanks. In this case, there are no permeability or deck tank factors to add, hence click OK to proceed.. 15
Step 8 in the wizard Create loading conditions A loading condition is set up by defining the draught, trim and heel Manually, often used to create a temporary equilibrium position prior to a stability analysis. From a known mass For this workshop, please use 5 m as draught 16
Step 9 in the wizard Create fluid properties There may be several fluid types that fill the compartments Examples may be water, oil, sea water In this workshop one fluid type is used define Sea_water with density 1025 kg/m 3 Click OK to proceed to next step Step 10 in the wizard Create flooded properties The flooding compartment property is used to specify whether a compartment is to be considered flooded or not Create one property for flooding as shown Click OK to proceed to next step 17
Step 11 in the wizard Specify filling fractions The filling fractions are used to specify the degree of filling for each compartment Remember, the compartment filling is built up from fluid property, permeability and filling For this workshop, specify 10 filling fractions 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 You may also edit these values from the browser... 18
Step 12 in the wizard Create the compartment content The content of the compartments is now defined, both for intact and damaged conditions Define as shown below Click OK to proceed 19
Step 13 in the wizard Cont d Display the tank filling You may edit the visual settings of the compartment content by using the Modeling Draw Style as shown. The panel model transparency has been set to 90% below (from the Modeling Draw Style dialog on the panel model) 20
Step 13 in the wizard Specify the mass Various ways of defining the mass The various options are shown below For this workshop, use From File and import the file HydroD_Stab_Ex1_T1.FEM stored under C:\Program Files (x86)\dnvgl\hydrod V4.7- **\UserExamples\Barge\inp A total mass of 9011 tonnes is now imported. In addition comes mass of fluid in tanks 21
Step 14 in the wizard Automatic compartment balancing HydroD may do a compartment balancing to ensure that the draft, trim and heel specified are met We select compartments 2, 3, 8 and 9 and press the Compute filling fractions button. 22
Step 14 cont. The filling fractions and compartment contents should now look like: 23
Step 15 in the wizard Define flooding openings You may specify flooding openings to track whether they are above or below the water surface during a hydrostatic computation and connect them to different compartments In this workshop 2 openings are defined, Point_1 and Point_2 at the barge corners as indicated The flooding openings are defined by graphic selection, but you may also enter the explicit coordinates No compartments are connected with openings in this workshop 24
Step 16 in the wizard Create stability analysis Define hydrostatic analysis with the purpose of computing GZ curves and other hydrostatic data. There may be many hydrostatic analyses reflecting various loading conditions and/or rotation axis. Typically there will be several loading conditions simulating various intact and damaged conditions. See later in this workshop how to make multiple loading conditions and hydrostatic analyses Make one loading condition as shown below 25
Step 17 in the wizard Create wind profile Wind influences stability as heeling moments and it is thus necessary to include it in the stability calculations. The wind contribution is a combination of wind profile, drag coefficients, block coefficients and active structure area. Wind profiles may be user defined or standard IMO MODU Wind Profile This tutorial assumes usage of standard wind profile with wind velocity 75 m/s The wind profiles may be edited from the browser as indicated below 26
Step 18 in the wizard Create drag coefficient curve Specify the drag coefficient curve as a relation between diameters and drag coefficients. 27
Step 19 in the wizard Create drag block coefficient curve Specify the drag block coefficient curve as a relation between cross sectional block coefficient and drag coefficients. Drag as function of cross-sectional area divided by circumscribed area (i.e. is it a round shape or is it something more square 28
Step 20 in the wizard Create heeling moment The heeling moment is now defined as a combination of: This heeling moment is perpendicular to the heeling axis You may also specify the wind heeling moments by a user definition This tutorial assumes empiric flow as defined above 29
Step 21 in the wizard Run the hydrostatic analysis 30
Step 22 in the wizard Look at the results Examples on results to look at the GZ curve You may find the exact GZ values for each angle by saving a report (File Save Report) or from information (right click an analysis and choose Information) Note that the z-level of the lowest flooding opening is displayed together with the GZ-curve 31
Step 22 in the wizard Examples on results to look at Moment of force You may compute the righting moment integral by changing start and end angles Note that for the 75m/s wind the overturning wind moment exceeds the righting moment (meaning that it will capsize)! 32
Step 22 in the wizard Examples on results to look at Flooding openings 33
Step 22 in the wizard Examples on results to look at Cross section data shear force 34
Step 22 in the wizard Examples on results to look at Cross section data bending moment 35
Step 22 in the wizard Examples on results to look at Model Information You find typical model data here More information will be produced by Save report 36
Part 2 New loading condition Copy the transit loading condition Right click the Transit loading condition in the browser and select Copy Right click the LoadingConditions folder and choose paste A new loading condition called Transit_1 should now emerge in the browser (inheriting the name from the original loading condition) 37
Part 2 New loading condition Change the compartment filling Right click the CompartmentContents2 folder and choose Compartment contents Change the filling fractions for compartment number 8 and 9 38
Part 2 New loading condition Recompute the equillibrium position Right click Transit_1 and choose Edit Press the Compute from mass button and compute the new equillibrium position based on the mass model Press OK to apply the new position 39
Part 3 Damaged loading condition Copy the Transit loading condition and damage compartments Again we start by copying the transit loading condition to create Transit_2 (right click Transit and choose Copy, right click LoadingConditions1 and choose Paste ) Rename the loading condition to TransitDamage Right click the CompartmentContents3 folder and choose Compartment contents Flood compartments 1 and 3 by selecting the flooded property and pressing OK 40
Part 3 Damaged loading condition Recompute the equillibrium position Select Edit on the TransitDamage loading condition and recompute the equilibrium position from the mass. Press OK. 41
Part 3 Damaged loading condition View the new equillibrium position. 42
Part 4 Multiple analysis Create stability analysis for the Transit_1 loading condition Right click StabilityTransit and choose Copy Right click the StablityAnalysis folder and choose Paste Select Edit on the new StabilityTransit_1 and change the loading condition. Press OK. 43
Part 4 Multiple analysis Create stability analysis for the TransitDamage condition Right click the StabilityAnalysis folder and choose New Stability Analysis Select loading conditions and location as shown below. Note that also the undamaged condition is specified. Press the Auto detect damage rotation axis to detect the rotation axis Make the remaining settings as below and press OK 44
Part 4 Multiple analysis Execute multiple analysis Right click the StabilityAnalysis folder and choose Execute Stability Analysis Select the analysis you want to execute by clicking on the icons in the list Press Start to execute 45
Part 4 Multiple analysis View the results As previously the results can be viewed from the stability report dialog reached by right clicking an analysis in the browser More details can be viewed by selecting Information on an analysis 46
Part 4 Multiple analysis View the results 47
Part 4 Multiple analysis View the results Note that the left browser pane tree can be expanded and more information is revealed 48
Part 4 Multiple analysis View the results The most extensive amount of information is created by save report (either from an object in the browser or from the File menu) We employ the XML word format 49
Part 5 Save the work Make a clean journal file Save the work for later use When save or exit, all data is stored and you can open the workspace later on Save the journal file for later use You can import the journal file created during this session into a new workspace. This file contains all historical data such as copy, rename and so on. It is recommended to make a Clean Journal file. This journal file will create a minimum of commands to regenerate the actual model. From the File Save Clean JS please give the name Transport_stability_in. You can look at this file it is stored on the project directory specified by you. The file may be edited and re-used in other projects 50