CFD Analysis Of a Commercial Vehicle

The following module learning outcomes and professional body learning outcomes are tested in this assessment:

(LO1) Construct appropriate solid models for CFD analysis, setup the solution domain and generate suitable surface and volume grids via meshing tool. (SM3m, SM5m)

(LO2) Understand both flow physics and mathematical properties of governing Navier-Stokes equations and define appropriate boundary conditions. (EA3m)

(LO3) Use CFD software to model flow problems of relevance to Mechanical Engineers. Analyse the CFD results and compare them with available data. (SM4m, EA1m, EA4m, EA5m, EA6m, D3m, EP4m)

(1) Please open the solid models in Solidworks and save them in Parasolid format before using in Ansys (as done in some tutorials). Modifications of the original solid model should be done in Ansys using Design Modeller, otherwise modifications could be not comptatible with Ansys. Calculations should be performed with fully three-dimensional model. To simplify meshing, you are allowed to introduce a small gap between the wheels and the ground. Kingston University cluster can be used as an option to speed up CFD calculations.

(2) You need to submit an electronic copy of the report in PDF format to Canvas for similarity and plagiarism checks. Please avoid MS Word file submission on Canvas because of some formatting issues with equations. Your work should be first fully word-processed (not handwritten and scanned) and then a copy saved as PDF for Canvas submission. Hardcopy not required. Do not include ANSYS WB files to the Canvas Submission.

(3) You need to upload an archived copy of your ANSYS WB files (.wbpz file) for Question 2 on Box and include the link in an appendix e.g. appendix A in your report.

(4) The maximum word limit for the report is 3000 words. Figures limits are specified in the relevant assignment sections. No other specific format is imposed.

(5) You should refer to the bibliographic sources you use in your assignment. A list of References must be presented at the end of the report listing all bibliographic sources cited, in Harvard style.

In this assignment you will use ANSYS Workbench and ANSYS CFX to investigate the aerodynamics of a commercial vehicle. The study is to be carried out on an accurate dimensional model of a standard 7.5 ton box van: 

Using the standard methodology described in the Tutorials sessions on external flow analysis as a guide, import the supplied model into ANSYS Workbench, set up the CFD model, solve it using ANSYS CFX and examine the characteristics of the flow. For the initial analysis, the model should be set up identically to the model investigated during the tutorial sessions except that the choice of the flow domain dimensions and inflation layers are for you to decide. In carrying out the modelling you should:

Module Learning Outcomes

Check the solid model and save it in a new format (if required).
Create the flow domain geometry and isolate the fluid region.
Identify and label the flow domain boundaries.
Set up the controlling parameters for surface and volume meshing.
Model the boundary layer using layer inflation.
Generate Preview Groups showing the mesh on key surfaces.
Generating the volume mesh.
Set up the physics of the flow and assign appropriate boundary conditions.
Set up the initial flow conditions and the solution monitors and controls.
Solve the model and monitor the solution convergence.
Create Contour, Streamline and Isosurface plots.
Assess the quality of the boundary layer modelling from the y+ distribution.
Use the CFX Function Calculator to determine lift and drag forces and coefficients.

Investigate the effect of domain size on your numerical results for lift and drag by varying the domain dimensions in a systematic way.

On completion of the analysis you should summarise your findings, and illustrate the general flow field around the bodyshell highlighting any problem areas or interesting flow features using combinations of appropriate Contour, Streamline and Isosurface plots. These plots should be produced in colour . No more than ten images should be provided and each one should be annotated and discussed to indicate the features you found to be of interest. Provide a clear statement of the results of your investigations into the effect of flow domain size and select suitable flow domain dimensions for Part 2.

Carry out some literature research into ways of improving the aerodynamics of commercial vehicles. Based on your research, choose two features you believe will improve the aerodynamic performance of the box van and describe why you believe that they will be effective.

Modify the given solid model to incorporate the features you have selected and re-do the CFD simulations and analysis of Part 1 for your modified model. In carrying out this additional analysis, there is no need to conduct further investigations into the effect of flow domain size. However, so that you can make direct comparisons between the results of PARTS1 & 2 and quantify the benefits achieved by your modifications, you should ensure that you use flow domain dimensions which you already used in PART1. Report the percentage reduction in the drag force achieved using your modified model. There is no specific target for the drag force but you need will to discuss any reduction or increase in the drag force on your modified model.As before, illustrate the flow field around the modified model using combinations of appropriate Contour, Streamline and Isosurface plots. All plots should be produced IN COLOUR. No more than ten images should be provided and again, each one should be annotated to indicate the features you found to be of
interest and to highlight any flow improvements you observe.

Provide a 3000-word report describing the results of your work.

The report should include all the plots you obtained in carrying out the work for Part 1 & 2, together with a clear table summarizingand comparing the numerical results for the drag and lift forces. The report should provide brief details of your modelling methodology together with a clear statement of all the flow domain dimensions and inflation layer you used. It should also describe the aerodynamic design elements you have incorporated in your improved box van model together with their engineering basis. By referring to the plots you obtained, link the aerodynamic design elements you incorporated to the flow features evident in the plots.

Provide a critical appraisal of the CFD modelling methodology you used for the assignment and discuss how it could be improved upon. Your discussion should  include comments on the appropriateness of the turbulence model used and on the quality of the boundary layer modelling achieved.

Note: In assessing your work, credit will be given for well thought out practical solutions showing technical engineering insight and understanding and for clarity of thought in both interpreting and presenting your results. Your report should be entirely in your own words. There should be no need for you to download large tracts of material from websites. No credit will be given for such material.