5 September 2002AIAA STC Meeting, Santa Fe, NM1 Verification and Validation for Computational Solid Mechanics Presentation to AIAA Structures Technical Committee Santa Fe, NM 6 September 2002 Ben Thacker Southwest Research Institute San Antonio, TX /

5 September 2002AIAA STC Meeting, Santa Fe, NM2 V&V Definitions Verification: Process of determining that a model implementation accurately represents the developer’s conceptual description of the model and the solution to the model Math issue: “Solving the equations right” Validation: Process of determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model Physics issue: “Solving the right equations”

5 September 2002AIAA STC Meeting, Santa Fe, NM3 Why do we need V&V? Reduced testing Higher performance requirements Drivers DOD Certification by Analysis DOE Stockpile Stewardship NRC High Level Radioactive Waste Repository …and more Philosophy, procedures and tools needed to support these efforts

5 September 2002AIAA STC Meeting, Santa Fe, NM4 ASME Committee for V&V in Computational Solid Mechanics ASME Standards committee formed Sept ‘01: “Verification and Validation in Computational Solid Mechanics” Charter To develop standards for assessing the correctness and credibility of modeling and simulation in computational solid mechanics Approach Guidelines  Recommended Practices  Standards

5 September 2002AIAA STC Meeting, Santa Fe, NM5 Verification and Validation Process Level 1 Diagram Confirmation Verification Validation REALITY OF INTEREST MATHEMATICAL MODEL COMPUTER MODEL Simulation Outcomes Modeling Software Implementation Modeling, Simulation, & Experimental Activities Assessment Activities

5 September 2002AIAA STC Meeting, Santa Fe, NM6 Verification and Validation Process Level 2 Diagram Experimental Design Confirmation Conceptual Model Confirmation Feature Extraction Software Implementation AnalysisData Reduction ModelingExperimentation Experimental Data Confirmation Experimental Feature Confirmation Code & Calculation Verification Mathematical Model Confirmation Model Validation REALITY OF INTEREST EXPERIMENTAL REALIZATION EXPERIMENTAL DATA EXPERIMENTAL FEATURES MATHEMATICAL MODEL COMPUTER MODEL CONCEPTUAL MODEL Modeling, Simulation, & Experimental Activities Assessment Activities UNCERTAINTY QUANTIFICATION

5 September 2002AIAA STC Meeting, Santa Fe, NM7 Verification Assessment Code Verification Purpose is to verify that the model is working as intended Mathematics issue Goal is to identify and eliminate errors Programming errors, incorrect input parameters, etc. Responsibility of the code developer Involves SQA, regression testing, etc.

5 September 2002AIAA STC Meeting, Santa Fe, NM8 Verification Assessment Calculation Verification Purpose is to verify that the model user can obtain correct solution to problems with known answers Mathematics issue Goal is to identify and eliminate errors Finite arithmetic, insufficient discretization or convergence, etc. Responsibility of the model user Involves comparing computational solutions with highly accurate solutions

5 September 2002AIAA STC Meeting, Santa Fe, NM9 Validation Assessment Goal is to increase confidence in the predictive capability of a model Objective is to quantify uncertainties and errors in the computational model and in the experimental measurements Physics issue Involves comparing computational solutions with validation experiments Unit problems, benchmark cases, subsystem cases, complete system A model is validated, not a code Must address different sources of uncertainty Inherent variations (irreducible or random uncertainty) Epistemic uncertainty (reducible or subjective uncertainty) Validation is application specific; does not address “adequacy” Specific domain of input parameters

5 September 2002AIAA STC Meeting, Santa Fe, NM10 Validation Testing Traditional experiments Improve fundamental understanding of physics Improve mathematical models Assess component or system performance Validation experiments Meant to measure with high accuracy one or more physics being modeled All assumptions must be understood and controlled (e.g., loading and boundary conditions) Should be conducted in hierarchal fashion (incrementally add physics) Keep test and predicted results separate until comparison No point in computing an answer you already know Sometimes the calculation will find an error in the experiment

5 September 2002AIAA STC Meeting, Santa Fe, NM11 Related Activities Pre-test Calcs, Model Updating & Adequacy Pre-test calculations Guide experiments Understand behavior Sensor placement Model/Test Updating Improve agreement Parameter calibration Increase fidelity Adequacy Application specific Domain dependent Accuracy dependent Feature Extraction Software Implementation Analysis Data Reduction ModelingExperimentation REALITY OF INTEREST EXPERIMENTAL REALIZATION EXPERIMENTAL DATA EXPERIMENTAL FEATURES MATHEMATICAL MODEL COMPUTER MODEL CONCEPTUAL MODEL PRE-TEST CALCS ADEQUATE? No UPDATE TEST UPDATE MODEL UNCERTAINTY QUANTIFICATION Yes VALID

5 September 2002AIAA STC Meeting, Santa Fe, NM12 Summary V&V is a process that stops when adequacy is reached Many aspects of V&V are research…opportunities for AIAA STC to get involved ASME V&V committee met at last year’s SDM and will meet at this years SDM (probably Sunday)…meeting is open to everyone