Code Verification, Solution Verification and Validation in RANS Solvers

2010 ◽  
Author(s):  
Lui´s Ec¸a ◽  
Guilherme Vaz ◽  
Martin Hoekstra
Keyword(s):  
Turbulent Flows ◽  
Verification And Validation ◽  
Test Cases ◽  
Simple Test ◽  
Error Evaluation ◽  
Code Verification ◽  
Engineering Activity ◽  
Solution Verification ◽  
The Right ◽  
Comparison With Experimental Data

The maturing of CFD codes for practical calculations of complex turbulent flows implies the need to establish the credibility of the results by Verification & Validation. These two activities have different goals: Verification is a purely mathematical exercise that intends to show that we are “solving the equations right”, whereas Validation is a science/engineering activity that intends to show that we are “solving the right equations”. Verification is in fact composed of two different activities: Code Verification and Solution Verification. Code Verification intends to verify that a given code solves correctly the equations of the model that it contains by error evaluation. On the other hand, Solution Verification intends to estimate the error of a given calculation, for which in general the exact solution is not known. Validation intends to estimate modelling errors by comparison with experimental data. The paper gives an overview of procedures for Code Verification, Solution Verification and Validation. Examples of the three types of exercises are presented for simple test cases demonstrating the advantages of performing Verification and Validation exercises.

Workshop on Verification and Validation of CFD for Offshore Flows

2012 ◽  
Author(s):  
L. Eça ◽  
G. Vaz
Keyword(s):  
Reynolds Numbers ◽  
Verification And Validation ◽  
Test Cases ◽  
Code Verification ◽  
Complex Flow ◽  
Solution Verification ◽  
Manufactured Solution ◽  
Cylinder Flow ◽  
Flow Case ◽  
Paper Submission

This document introduces the Workshop on Verification and Validation (V&V) of CFD for Offshore Flows, to be held during OMAE2012. It presents a brief introduction to the purpose of Verification and Validation with the identification of the goals of code and solution verification and validation. Within this context, three test-cases are proposed: Case-I of code verification, Case-II of solution verification and Case-III of solution verification and validation. Case-I consists on a 3D manufactured solution of an unsteady turbulent flow. Case-II is an exercise on the canonical problem of the infinite smooth circular cylinder flow at different Reynolds numbers. Case-III is a more complex flow around a straked-riser. The participants are asked to perform at least one of these test-cases. The objectives for the three proposed test-cases are presented, together with a detailed description of the numerical settings to be used, and the results to be obtained and sent to the Workshop organization. At the end some considerations on general conditions, paper submission, deadlines, and encouragements are stated.

scholarly journals Survey on Various Testing Techniques and Strategies for Bug Finding

2013 ◽  
Vol 11 (1) ◽  
pp. 2150-2155
Author(s):  
Mohit Kumar ◽  
Geetika Gandhi ◽  
Sushil Garg
Keyword(s):  
Software Testing ◽  
Verification And Validation ◽  
Test Cases ◽  
Validation Process ◽  
Software Product ◽  
Bug Finding ◽  
Testing Techniques ◽  
The Right ◽  
Selection Of

Software testing is verification and validation process aimed for evaluating a program and ensures that it meets the required result. The main goal of software testing is to uncover the errors in software. So the main aim of test cases is to derive set of tests that have highest probability of finding bugs. There are many approaches to software testing, but effective testing of any software product is essentially a tough process. It is nearly impossible to find all the errors in the program. The major problem in testing is what would be the strategy that we should adopt for testing. Thus, the selection of right strategy at the right time will make the software testing efficient and effective. In this paper I have described software testing techniques which are classified by purpose.

Effective Use of V&V20 Solution Verification Methodology

2010 ◽  
Author(s):  
Christopher J. Freitas
Keyword(s):  
Heat Transfer ◽  
Verification And Validation ◽  
Code Verification ◽  
Flow And Heat Transfer ◽  
Time Period ◽  
Solution Verification ◽  
Particular Solution ◽  
American Society ◽  
Effective Use ◽  
Verification Methodology

Methods for the quantification of numerical uncertainty have been a subject of interest to the American Society of Mechanical Engineers (ASME) and the mechanical engineering community as a whole for over a decade. During this time period, ASME has promulgated three statements of standards for the reporting of numerical uncertainty in archival publications (Journal of Fluids Engineering). This paper summarizes the work that has gone into the specification of these standards and the continuing effort in formulation of methods and procedures for quantifying numerical uncertainty. Specifically, this paper discusses the efforts of the ASME V&V 20 Committee (Verification and Validation in Computational Fluid Dynamics and Heat Transfer) to lay a foundation and structure to verification and validation for fluid flow and heat transfer simulations. Issues and methods related to code verification and in particular solution verification are presented and discussed in the context of the recently released V&V20 Standard.

An Example of Code Verification in the Simulation of Wave Propagation

2011 ◽  
Author(s):  
Fahd Fathi ◽  
Lui´s Ec¸a ◽  
Mart Borsboom
Keyword(s):  
Wave Propagation ◽  
Numerical Solution ◽  
Physical Reality ◽  
Verification And Validation ◽  
Cfd Modeling ◽  
Code Verification ◽  
Complex Flows ◽  
Solution Verification ◽  
The Mathematical Model

Thanks to advances in modeling and hardware the range of applications available to CFD modeling is continuously increasing. As CFD has moved from demonstration of capability to production of engineering results of practical value, there is an increased awareness in the field that Verification and Validation are systematically required. Verification deals with the numerical accuracy of a given set of results. Its object is the assessment of the numerical uncertainty due to discretization and iterative errors of a numerical solution (Solution Verification) performed with a Code that has been previously checked to be free of errors (Code Verification). Both activities are required to ensure that errors are controlled and that quality of the results is maintained. Complementarily, Validation addresses the modeling error, i.e. the comparison of the mathematical model with the (physical) reality. Therefore, it requires comparison with experimental data. Validating CFD results is only meaningful when preceded by carefully verified calculations (Solution Verification) with verified codes (Code Verification). The topic of Verification and Validation is developing and standardized procedures are still under discussion. Nevertheless, there are techniques available to perform careful Code and Solution Verification for flows with engineering relevance. This paper presents a Code Verification exercise for the simulation of wave propagation with a VOF code. Systematically refined grids and time steps are applied in the calculation of waves with a known analytical solution to assess the convergence properties of the numerical solution. The aim of the exercise is to demonstrate the advantages of such exercises for the knowledge of the numerical properties of a code that is applied in complex flows. The study is not a pure Code Verification exercise. Modeling errors introduced by approximate outlet boundary conditions (allowing wave reflections) are also quantified for a linear and a high-order wave. However, these are still based on (numerical) error evaluations for known analytical solutions and so they can still be classified as Code Verification.

A Three-Equation Eddy-Viscosity Model for Reynolds-Averaged Navier–Stokes Simulations of Transitional Flow

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
D. Keith Walters ◽  
Davor Cokljat
Keyword(s):  
Boundary Layer ◽  
Turbulent Flows ◽  
Eddy Viscosity ◽  
Flow Behavior ◽  
Applied Pressure ◽  
Plate Boundary ◽  
Low Frequency ◽  
Transitional Flow ◽  
Test Cases ◽  
Eddy Viscosity Model

An eddy-viscosity turbulence model employing three additional transport equations is presented and applied to a number of transitional flow test cases. The model is based on the k-ω framework and represents a substantial refinement to a transition-sensitive model that has been previously documented in the open literature. The third transport equation is included to predict the magnitude of low-frequency velocity fluctuations in the pretransitional boundary layer that have been identified as the precursors to transition. The closure of model terms is based on a phenomenological (i.e., physics-based) rather than a purely empirical approach and the rationale for the forms of these terms is discussed. The model has been implemented into a commercial computational fluid dynamics code and applied to a number of relevant test cases, including flat plate boundary layers with and without applied pressure gradients, as well as a variety of airfoil test cases with different geometries, Reynolds numbers, freestream turbulence conditions, and angles of attack. The test cases demonstrate the ability of the model to successfully reproduce transitional flow behavior with a reasonable degree of accuracy, particularly in comparison with commonly used models that exhibit no capability of predicting laminar-to-turbulent boundary layer development. While it is impossible to resolve all of the complex features of transitional and turbulent flows with a relatively simple Reynolds-averaged modeling approach, the results shown here demonstrate that the new model can provide a useful and practical tool for engineers addressing the simulation and prediction of transitional flow behavior in fluid systems.

Large-Eddy Simulations of Wall Bounded Turbulent Flows Using Unstructured Linear Reconstruction Techniques

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Dario Amirante ◽  
Nicholas J. Hills
Keyword(s):  
Reynolds Number ◽  
Turbulent Flows ◽  
Outer Radius ◽  
Large Eddy Simulations ◽  
Test Cases ◽  
Mean Flow ◽  
Flow Equations ◽  
Turbulent Statistics ◽  
Large Eddy ◽  
Least Squares Approach

Large-eddy simulations (LES) of wall bounded, low Mach number turbulent flows are conducted using an unstructured finite-volume solver of the compressible flow equations. The numerical method employs linear reconstructions of the primitive variables based on the least-squares approach of Barth. The standard Smagorinsky model is adopted as the subgrid term. The artificial viscosity inherent to the spatial discretization is maintained as low as possible reducing the dissipative contribution embedded in the approximate Riemann solver to the minimum necessary. Comparisons are also discussed with the results obtained using the implicit LES (ILES) procedure. Two canonical test-cases are described: a fully developed pipe flow at a bulk Reynolds number Reb = 44 × 103 based on the pipe diameter, and a confined rotor–stator flow at the rotational Reynolds number ReΩ = 4 × 105 based on the outer radius. In both cases, the mean flow and the turbulent statistics agree well with existing direct numerical simulations (DNS) or experimental data.

scholarly journals The Right to Know and the Right Not to Know Revisited: Part One

2017 ◽  
Vol 9 (1-2) ◽  
pp. 3-18 ◽  
Author(s):  
Roger Brownsword ◽  
Jeff Wale
Keyword(s):  
Genetic Information ◽  
Human Genetics ◽  
Prenatal Testing ◽  
Test Cases ◽  
Right To Know ◽  
Non Invasive ◽  
The Right To Know ◽  
Right Not To Know ◽  
The Uk ◽  
The Right

Abstract Prompted by developments in human genetics, a recurrent bioethical question concerns a person’s ‘right to know’ and ‘right not to know’ about genetic information held that is intrinsically related to or linked to them. In this paper, we will revisit the claimed rights in relation to two particular test cases. One concerns the rights of the 500,000 participants in UK Biobank (UKB) whose biosamples, already having been genotyped, will now be exome sequenced, and the other concerns the rights of pregnant women (and their children) who undergo non-invasive prenatal testing (NIPT)—a simple blood test that can reveal genetic information about both a foetus and its mother. This two-part paper is in four principal sections. First, we sketch the relevant features of our two test cases. Secondly, we consider the significance of recent legal jurisprudence in the UK and Singapore. Thirdly, we consider how, the jurisprudence apart, the claimed rights might be grounded. Fourthly, we consider the limits on the rights. We conclude with some short remarks about the kind of genetically aware society that we might want to be and how far there is still an opportunity meaningfully to debate the claimed rights.

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