Advances in scientific computing have made modelling and simulation an important part of the decision-making process in engineering, science, and public policy. This book provides a comprehensive and systematic development of the basic concepts, principles, and procedures for verification and validation of models and simulations. The emphasis is placed on models that are described by partial differential and integral equations and the simulations that result from their numerical solution. The methods described can be applied to a wide range of technical fields, from the physical sciences, engineering and technology and industry, through to environmental regulations and safety, product and plant safety, financial investing, and governmental regulations. This book will be genuinely welcomed by researchers, practitioners, and decision makers in a broad range of fields, who seek to improve the credibility and reliability of simulation results. It will also be appropriate either for university courses or for independent study.

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Verification and Validation in Scientific Computing

Review of code and solution verification procedures for computational simulation

https://cfwebprod.sandia.gov/cfdocs/CompResearch/docs/Oberkampf-Trucano-SAND2007-0853.pdf

Verification and validation benchmarks

Review and assessment of turbulence models for hypersonic flows

The second AIAA CFD High-Lift Prediction Workshop was held in San Diego, California, in June 2013. The goals of the workshop continued in the tradition of the first high-lift workshop: to assess the numerical prediction capability of current-generation computational fluid dynamics (CFD) technology for swept, medium/high-aspect-ratio wings in landing/takeoff (high-lift) configurations. This workshop analyzed the flow over the DLR-F11 model in landing configuration at two different Reynolds numbers. Twenty-six participants submitted a total of 48 data sets of CFD results. A variety of grid systems (both structured and unstructured) were used. Trends due to grid density and Reynolds number were analyzed, and effects of support brackets were also included. This paper analyzes the combined results from all workshop participants. Comparisons with experimental data are made. A statistical summary of the CFD results is also included.

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Overview and Summary of the Third AIAA High Lift Prediction Workshop.

The method of manufactured solutions is used to verify the order of accuracy of two finite-volume Euler and Navier–Stokes codes. The Premo code employs a node-centred approach using unstructured meshes, while the Wind code employs a similar scheme on structured meshes. Both codes use Roe's upwind method with MUSCL extrapolation for the convective terms and central differences for the diffusion terms, thus yielding a numerical scheme that is formally second-order accurate. The method of manufactured solutions is employed to generate exact solutions to the governing Euler and Navier–Stokes equations in two dimensions along with additional source terms. These exact solutions are then used to accurately evaluate the discretization error in the numerical solutions. Through global discretization error analyses, the spatial order of accuracy is observed to be second order for both codes, thus giving a high degree of confidence that the two codes are free from coding mistakes in the options exercised. Examples of coding mistakes discovered using the method are also given. Copyright © 2004 John Wiley & Sons, Ltd.

Verification of Euler/Navier–Stokes codes using the method of manufactured solutions

This paper presents the results of fixed grid RANS turbulence model investigation performed with Simcenter STAR-CCM+ for the 4th AIAA High Lift Prediction Workshop. The analysis focuses on prediction of the maximum lift and understanding the different factors that have impact on near-stall simulation. The presented discussion includes validation of the SA model implementation available in Simcenter STAR-CCM+ executed on different grid families. The verification study demonstrates the impact of the chosen grid topology on the verification results and the changes in the simulation behavior depending on the choice of the turbulence model. The observations from the verification study are consistent with the nominal angle of attack results on the high lift Common Research Model, with Lag EB model predicting the highest lift. Obtained force coefficient polars show similar force values for different methods at low incidences and a large spread in the predicted forces close to the stall angle. The pitching moment coefficient predictions are most sensitive to the choice of the turbulence model even at the nominal angles of attack, with only the Lag EB model predicting values similar to the experimental data. The modified SST model predicts the lift behavior up to the wing stall. Lag EB results follow the experiment but separate prematurely due to wing-root junction separation. Runs using SA are dominated by outboard wing separation and fail to match the experiment. The presented work demonstrates that RANS can be used to successfully predict both integrated quantities and flow behaviors for high-lift configurations at low-to-moderate angles of attack, provided that adequate turbulence modelling is used. RANS can also predict the correct stall mechanisms but not the exact angle at which stall occurs. 

Fixed Grid RANS Results and Turbulence Model Investigation using Simcenter STAR-CCM+ for 4thAIAA CFD High Lift Prediction Workshop

Using the Simcenter STAR-CCM+ commercial multiphysics software, an optimization study has been conducted to identify an improved nacelle design for the Eclipse business jet. The complete full-sized vehicle was included in the simulations (with flaps up and landing gear stowed). The optimization addressed multiple objectives and constraints, which represent the critical performance criteria. In addition, multiple flight conditions were considered in order to cover all the vital portions of the flight envelope. The optimal design yielded better performance for all objectives at all flight conditions and satisfied the constraints as well. In particular, the cruise drag was predicted to be improved by more than 14 percent compared to the baseline configuration. A follow-up validation effort was conducted to ensure that the results were not due to numerical problems with the analysis. Issues addressed included the impact of turbulence modeling, near-wall spacing, and overall mesh dependency. In all the tests, while there was some fluctuation of absolute values, the relative benefit derived from the best design compared to the original design remained consistent. This proof-of-concept study illustrates that practical design optimization is now within reach for production engineering organizations using commercially available software. 

Optimization of Nacelle Design and Integration on the Eclipse Business Jet


 The effect of blade tip planform on rotor aerodynamics in hover and forward flight is investigated. This work is based a set of test data for several advanced planforms, with the S-76 rotor serving as the baseline. Two complementary numerical modeling approaches - a hybrid Navier-Stokes/free wake approach, and a wake capturing approach - are used to study the rotor aerodynamics in hover and forward flight. The present studies indicate that the rotor hover performance, as measured by the required power for a specified thrust setting, improves when anhedral is introduced. Anhedral rotors are seen to produce a smother blade loading and a more uniform inflow, which is expected to result in reduced induced power for a given thrust loading. In forward flight, the anhedral tip behaves similarly to the baseline swept tapered tip, and the benefits of the anhedral tip are less pronounced due to the decreasing contribution of induced power to the total power consumption.


C. C. Nelson

Papers

Verification of Euler/Navier–Stokes codes using the method of manufactured solutions

Fixed Grid RANS Results and Turbulence Model Investigation using Simcenter STAR-CCM+ for 4thAIAA CFD High Lift Prediction Workshop

Optimization of Nacelle Design and Integration on the Eclipse Business Jet

Effects of Anhedral Tip on Forward Flight Performance