Assessment of the Academic CFD Code Galatea-I With the DARPA SUBOFF Test Case

In this study an academic CFD code, named Galatea-I, is presented, capable for simulating inviscid, viscous laminar and viscous turbulent incompressible fluid flows. It employs the RANS (Reynolds-Averaged Navier-Stokes) approach along with the SST (Shear Stress Transport) turbulence model to predict turbulent flow phenomena, such as recirculations and separations of flow, on three-dimensional unstructured hybrid grids, composed of prismatic, tetrahedral and pyramidal elements. Discretization of the governing equations is obtained with a node-centered finite-volume scheme. Parallel processing and agglomeration multigrid scheme are implemented for the acceleration of the numerical process. As the title of this paper reveals, the solver is validated against the test cases of the DARPA SUBOFF program; in particular, flows over the SUBOFF bare hull submarine geometry at two incident angles and the SUBOFF hull with fairwater configuration are examined. The obtained results, compared to available in open literature experimental data as well as results computed by reference solvers, indicate the proposed methodology’s potential to accurately simulate complex fluid flows.

LARGE EDDY SIMULATION OF TURBULENT INCOMPRESSIBLE FLUID FLOWS BY A NINE-NODES CONTROL VOLUME-FINITE ELEMENT METHOD

The main purpose of this work is the numerical computation of turbulent incompressible fluid flows by a nine-node control volume finite element method (CVFEM) using the methodology of large-eddy simulation.. The domain is discretized using nine nodes finite elements and the equations are integrated into control volumes around the nodes of the finite elements. The Navier?Stokes equations are filtered for simulation of the large scales variables and the sub-grid scales stress appearing due to the filtering process are modeled through the eddy viscosity model of Smagorinsky. The two-dimensional benchmark problem of the lid-driven cavity flow is solved to validate the numerical code and preliminary results for the horizontal and vertical velocity profiles at the centerlines of the cavity and the stream functions are presented and compared with available results from the literature.

LARGE EDDY SIMULATION OF TURBULENT INCOMPRESSIBLE FLUID FLOWS BY A NINE-NODES CONTROL VOLUME-FINITE ELEMENT METHOD

The main purpose of this work is the numerical computation of turbulent incompressible fluid flows by a nine-node control volume finite element method (CVFEM) using the methodology of large-eddy simulation.. The domain is discretized using nine nodes finite elements and the equations are integrated into control volumes around the nodes of the finite elements. The Navier?Stokes equations are filtered for simulation of the large scales variables and the sub-grid scales stress appearing due to the filtering process are modeled through the eddy viscosity model of Smagorinsky. The two-dimensional benchmark problem of the lid-driven cavity flow is solved to validate the numerical code and preliminary results for the horizontal and vertical velocity profiles at the centerlines of the cavity and the stream functions are presented and compared with available results from the literature.

INCOMPRESSIBLE FLUIDS

We propose a model for random forces in a turbulent incompressible fluid by balancing the energy gain from fluctuations against dissipation by viscosity. This leads to a more singular covariance distribution for the random forces than is ordinarily allowed. We then propose regularization of the fluid system by matrix models. A formula for entropy of a two dimensional fluid is derived and then a vorticity profile of a hurricane that maximizes entropy. A regularization of three dimensional incompressible fluid flow using quantum groups is also proposed.

Numerical Analysis of Turbulent Flow Along an Abruptly Rotated Cylinder

A parabolic system of equations governing turbulent, incompressible fluid motion along a stationary cylinder fitted with a rotating aft-section is solved with an implicit finite-difference algorithm. The mean flow is steady, axisymmetric, and characterized by abrupt skewing of the boundary layer. The equations of mean motion are closed with an eddy viscosity model based on Cebeci’s axisymmetric formulation. The analysis is compared with the experimental results of Bissonnette and Mellor, who have obtained data for ratios of cylinder wall speed to free-stream speed equal to 0.936 and 1.800. Predicted components of wall shear stress agree with the experimental values within the uncertainty associated with the experiment, and early boundary-layer development is predicted reasonably well. However, the analysis fails to predict the experimentally observed acceleration of the mean, axial flow.