Approach for uncertainty propagation and design in Saint Venant equations via automatic sensitive derivatives applied to Saar river

2009 ◽  
Vol 36 (7) ◽  
pp. 1144-1154 ◽  
Author(s):  
Otmane Souhar ◽  
Jean-Baptiste Faure
Keyword(s):  
Automatic Differentiation ◽  
Divided Difference ◽  
Uncertainty Propagation ◽  
Free Surface Flows ◽  
Cfd Simulations ◽  
Surface Flows ◽  
One Dimensional ◽  
Saint Venant Equations ◽  
Computational Fluid Dynamics Cfd ◽  
Derivatives Of

This paper describes the assessment of uncertainties of computational fluid dynamics (CFD) for modelling free surface flows. A series of CFD simulations, using MAillé GEnéralisé (MAGE), are employed to compute the flood extent resulting from the overflow of rivers. These simulated outputs are affected by uncertainties in the empiric roughness coefficients. Uncertainty propagation in MAGE outputs is difficult to evaluate because of the complexity and the nonlinearity of models. Assessment of uncertainties may be carried out by computing derivatives of the output results with respect to the inputs. Recently, automatic differentiation (AD) has become an efficient numerical method for sensitivity analysis and assessment of uncertainties. In this paper, AD is used to transform mechanically a given one-dimensional hydraulic model, MAGE, into a new program capable of computing the original simulation and the desired derivatives. Specifically, derivatives of the flood extent and the water width with respect to the roughness coefficients are computed. Numerical experiments of derivatives obtained from AD and divided difference (DD) approximations are compared, validating derivatives obtained by AD. Results can serve to evaluate existing flood models.

scholarly journals Probabilistic Performance Analysis of Eroded Compressor Blades

2005 ◽  
Author(s):  
A. Kumar ◽  
P. B. Nair ◽  
A. J. Keane ◽  
S. Shahpar
Keyword(s):  
Probabilistic Analysis ◽  
Surrogate Model ◽  
Uncertainty Propagation ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Compressor Blades ◽  
Geometry Modeling ◽  
Blade Section ◽  
Computational Fluid Dynamics Cfd ◽  
Fan Blade

This paper presents a probabilistic analysis of the effect of erosion on the performance of compressor fan blades. A realistic parametric CAD model is developed to represent eroded blades. Design of Experiments (DOE) techniques are employed to generate a set of candidate points, which are combined with a parametric geometry modeling and grid generation routine to produce a hybrid mesh. A multigrid Reynolds-Averaged Navier Stokes (RANS) solver HYDRA with Spalart Allmaras turbulence model is used for Computational Fluid Dynamics (CFD) simulations. The data generated is used to create a surrogate model for efficient uncertainty propagation. This method is applied to a typical Rolls Royce compressor fan blade section. Monte Carlo Simulation, using the surrogate model, is executed for the probabilistic analysis of the compressor fan blade. Results show upto 5% increase in pressure loss for the eroded compressor fan blades.

Application of a new drag coefficient model at CFD-simulations on free surface flows relevant for the nuclear reactor safety analysis

2012 ◽  
Vol 39 (1) ◽  
pp. 70-82 ◽  
Author(s):  
Deendarlianto ◽  
Thomas Höhne ◽  
Pavel Apanasevich ◽  
Dirk Lucas ◽  
Christophe Vallée ◽  
...  
Keyword(s):  
Free Surface ◽  
Drag Coefficient ◽  
Nuclear Reactor ◽  
Safety Analysis ◽  
Free Surface Flows ◽  
Reactor Safety ◽  
Cfd Simulations ◽  
Surface Flows ◽  
Nuclear Reactor Safety

scholarly journals Adjoint-Based Aerodynamic Design of Complex Aerospace Configurations

2016 ◽  
Author(s):  
Eric J. Nielsen
Keyword(s):  
Large Scale ◽  
Design Research ◽  
Design Parameters ◽  
Aerodynamic Design ◽  
Cfd Simulations ◽  
Sensitivity Derivatives ◽  
Computational Fluid Dynamics Cfd ◽  
Langley Research Center ◽  
The Cost ◽  
Derivatives Of

An overview of twenty years of adjoint-based aerodynamic design research at NASA Langley Research Center is presented. Adjoint-based algorithms provide a powerful tool for efficient sensitivity analysis of complex large-scale computational fluid dynamics (CFD) simulations. Unlike alternative approaches for which computational expense generally scales with the number of design parameters, adjoint techniques yield sensitivity derivatives of a simulation output with respect to all input parameters at the cost of a single additional simulation. With modern large-scale CFD applications often requiring millions of compute hours for a single analysis, the efficiency afforded by adjoint methods is critical in realizing a computationally tractable design optimization capability for such applications.

scholarly journals ADIFOR–Generating Derivative Codes from Fortran Programs

1992 ◽  
Vol 1 (1) ◽  
pp. 11-29 ◽  
Author(s):  
Christian Bischof ◽  
Alan Carle ◽  
George Corliss ◽  
Andreas Griewank ◽  
Paul Hovland
Keyword(s):  
Data Analysis ◽  
Automatic Differentiation ◽  
Divided Difference ◽  
Real Life ◽  
Programming Environment ◽  
Critical Importance ◽  
Difference Approximations ◽  
Source Transformation ◽  
Derivatives Of ◽  
Fortran 77

The numerical methods employed in the solution of many scientific computing problems require the computation of derivatives of a function f Rn→Rm. Both the accuracy and the computational requirements of the derivative computation are usually of critical importance for the robustness and speed of the numerical solution. Automatic Differentiation of FORtran (ADIFOR) is a source transformation tool that accepts Fortran 77 code for the computation of a function and writes portable Fortran 77 code for the computation of the derivatives. In contrast to previous approaches, ADIFOR views automatic differentiation as a source transformation problem. ADIFOR employs the data analysis capabilities of the ParaScope Parallel Programming Environment, which enable us to handle arbitrary Fortran 77 codes and to exploit the computational context in the computation of derivatives. Experimental results show that ADIFOR can handle real-life codes and that ADIFOR-generated codes are competitive with divided-difference approximations of derivatives. In addition, studies suggest that the source transformation approach to automatic differentiation may improve the time to compute derivatives by orders of magnitude.

scholarly journals Simulation of complex free surface flows

2021 ◽  
Vol 70 ◽  
pp. 45-67
Author(s):  
Krisztian Benyo ◽  
Ayoub Charhabil ◽  
Mohamed-Ali Debyaoui ◽  
Yohan Penel
Keyword(s):  
Free Surface ◽  
Free Surface Flows ◽  
Secondary Wave ◽  
Solitary Wave Solutions ◽  
Splitting Scheme ◽  
Surface Flows ◽  
Iterative Correction ◽  
Pressure Term ◽  
Difference Type ◽  
Saint Venant Equations

We study the Serre-Green-Naghdi system under a non-hydrostatic formulation, modelling incompressible free surface flows in shallow water regimes. This system, unlike the well-known (nonlinear) Saint-Venant equations, takes into account the effects of the non-hydrostatic pressure term as well as dispersive phenomena. Two numerical schemes are designed, based on a finite volume - finite difference type splitting scheme and iterative correction algorithms. The methods are compared by means of simulations concerning the propagation of solitary wave solutions. The model is also assessed with experimental data concerning the Favre secondary wave experiments [12].

Modeling and Simulation of Capillary Microfluidic Networks Based on Electrical Analogies

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Seok-Won Kang ◽  
Debjyoti Banerjee
Keyword(s):  
Flow Characteristics ◽  
Free Surface Flows ◽  
Network Simulator ◽  
Cfd Simulations ◽  
Simulation Techniques ◽  
Filling Time ◽  
Microfluidic Networks ◽  
Lumped Models ◽  
Computational Fluid Dynamics Cfd ◽  
Volume Of Fluids

In this study we implemented the network simulation techniques using macromodels (lumped models) for capillary driven flows in microfluidic networks. The flow characteristics in a flow junction, such as meniscus stretching and bifurcation, were studied and their effects on filling time as well as pressure drop were explored for various network configurations. The results from the network simulator are validated numerically using computational fluid dynamics (CFD) simulations by employing the volume-of-fluids (VOF) method. The predictions by the network simulator for free-surface flows in different microfluidic networks were found to be in good agreement with the results obtained from the VOF simulations for filling time and meniscus position.

scholarly journals Numerical and One-Dimensional Studies of Supersonic Ejectors for Refrigeration Application: The Significance of Wall Pressure Variation in the Converging Mixing Section

2021 ◽  
Vol 11 (7) ◽  
pp. 3245
Author(s):  
Eldwin Djajadiwinata ◽  
Shereef Sadek ◽  
Shaker Alaqel ◽  
Jamel Orfi ◽  
Hany Al-Ansary
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Experimental Work ◽  
Pressure Variation ◽  
The Other ◽  
Dimensional Model ◽  
Cfd Simulations ◽  
One Dimensional ◽  
Supersonic Ejector ◽  
Computational Fluid Dynamics Cfd

This paper studies the pressure variation that exists on the converging mixing section wall of a supersonic ejector for refrigeration application. The objective is to show that the ejector one-dimensional model can be improved by considering this wall’s pressure variation which is typically assumed constant. Computational Fluid Dynamics (CFD) simulations were used to obtain the pressure variation on the aforementioned wall. Four different ejectors were simulated. An ejector was obtained from a published experimental work and used to validate the CFD simulations. The other three ejectors were a modification of the first ejector and used for the parametric study. The secondary mass flow rate,

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