Jules W. Lindau

Pennsylvania State University | Penn State · Applied Research Laboratory

The understanding of the internal gaseous flow of artificially ventilated supercavities is developed using a locally homogenous, multiphase computational fluid dynamics model that is benchmarked using experimental data. The solutions indicate that gas leakage from a ventilated supercavity originates from the gaseous shear layers forming at the gas-...

In this work, the character of the pressure within artificially ventilated cavities is investigated in detail using computational fluid dynamics. The efforts explore the details of the pressure inside both twin- and toroidal-vortex cavities through histograms of the internal cavity pressure. Rather than a uniform pressure, detailed interrogation of...

This effort investigates advancing cavitation modeling relevant to computational fluid dynamics (CFD) through two strategies. The first aims to reformulate the cavitation models and the second explores adding liquid-vapor slippage effects. The first aspect of the paper revisits cavitation model formulations with respect to the Rayleigh-Plesset equa...

In this work, an alternate level-set-based approach is presented that applies uniformly to compressible and incompressible multiphase flows. Fundamental to this work, is the development of analytic transformations from a signed-distance function to species-mass conservation variables. Such transformations can be used to highlight compressible flow...

Computational Fluid Dynamics (CFD) is employed to study the fundamental aspects of the internal pressure within artificially ventilated, gaseous cavities in both twin- and toroidal-vortex closure modes. The results show that several pressure regions develop within the cavities, indicating that the common assumption that the cavity has a constant pr...

The dynamics of gas jets expelled into liquid are investigated utilizing Computational Fluid Dynamics (CFD). Results are analyzed with respect to changes in external liquid velocity and mass flow rate of the gaseous jet. In order categorize the complicated nature of the gas-fluid interactions coupled with the many physical dependencies, a flow-regi...

The present paper aims to close the gap on the understanding of cavitation model performance with respect to their inherent empirical constants. We first unify several cavitation models, providing a consistent framework for model comparison. Analytical methods are developed to directly compare cavitation models to the Rayleigh Plesset equation. The...

Computations of pulsating supercavity flows behind axisymmetric disk cavitators are presented. The method of computation is a finite volume discretization of the equations of mixture fluid motion. The gas phase is treated as compressible, the liquid phase as incompressible, and the interface accuracy enhanced using a volume of fluid approach. The r...

Finite volume based modeling of ventilated supercavity pulsation and its mitigation via a priori modulation of ventilation flow was investigated. Simulated pulsation was numerically achieved, as was mitigation of pulsation via sinusoidal modulation of the ventilation flow. In addition to confirmation that the numerical approach is sufficient to cap...

A method for mitigating ventilated supercavity pulsation is presented. The method, which has its roots in parametric oscillators, shifts the supercavity resonance frequency by modulating its gas ventilation rate. When appropriately modulated, the supercavity is driven off resonance by the waves on the gas/water interface (that remain unchanged) and...

The noise radiated by pulsating supercavities has been measured in a water tunnel facility. The noise was found to be single frequency and monopole in nature with a spectrum level given by the level of the cavity interior pressure and attenuation due to spherical spreading from the interface. The radiated noise levels from pulsating supercavities w...

Steady-periodic multiphase Computational Fluid Dynamics (CFD) simulations were conducted to capture cavitation breakdown in a Francis hydroturbine due to large-scale vaporous structures. A reduced-scale model and a full-scale prototype were investigated to display differences in vapor content and machine performance caused by lack of Reynolds and F...

The noise generated by ventilated supercavities has been explored experimentally in a water tunnel facility. The most prominent acoustical characteristic is the monopole behavior exhibited by a ventilated supercavity in its pulsating closure regime. The interior cavity pressure and near-field radiated sound are monotonic with a frequency that is re...

RANS and LES modeling are applied to the geometrically complex problem of glaze ice accretion on fixed-wing and rotorcraft airfoils. The shortcomings of transport based RANS turbulence models for these systems is demonstrated using three experimental data sets. The roles of meshing topology, turbulence model choice, and 2D assumptions are quantifie...

A computational-fluid-dynamics-based modeling effort to capture flow through an axial flow waterjet propulsor is presented. The effort covered the waterjet flow over a wide range of flow coefficients and into cavitation-driven breakdown. The computations are presented in cavitation at two values of flow coefficient through a series of decreasing op...

The importance of modeling thermal effects in cavitatingfluid is examined in the context of computational fluid dynamics. Simulations of cavitation in water are used to study the effects of thermal versus and pressure variations in the fluid properties, and their impact on predictions. These studies are extended to evaluate energyconserving approac...

Using multiphase computational simulations based on the Navier-Stokes equations, we examine the internal gaseous flows of artificially ventilated supercavities. These simulations indicate that air shear layers that develop on the cavity-wall (the air-liquid interface surrounding the cavity) are an important mechanism of air entrainment. This corrob...

Computational fluid dynamics (CFD) simulations are prone to inaccuracies associated with incorrectly formulated physical models. Common in CFD is the spurious treatment as locally laminar flow regions as turbulent, resulting in incorrect turbulent-boundary-layer profiles, separated-flow behavior, and local skin-friction coefficients. The combined e...

In this work, a new level-set-based approach is presented and applied to compressible, multiphase flows. Using a species-mass-conservation-based level-set transport equation, several advantages over signed-distance-function- based methods are demonstrated. Specific improvements include a ghost-fluid-free method for highly compressible problems, ext...

In this work, a new level-set-based approach is presented and applied to compressible, multiphase flows. Using a species-mass-conservation-based level-set transport equation, several advantages over signeddistance- function-based methods are demonstrated. Specific improvements include a ghost-fluid-free method for highly compressible problems, exte...

This paper summarizes a number of large-scale multiphase computation fluid dynamics (CFD) analyses of relevance to the Defense Advanced Research Projects Agency (DARPA) Underwater Express Program. The specific focus of this paper is on developed and supercavitating configurations related to submerged vehicles and control surfaces where proximity to...

A complete physical model of ventilated supercavitation is not well established. Efforts documented display the ability, with a finite volume, locally homogeneous approach, to simulate supercavitating flows and obtain good agreement with experiments. Several modeling requirements appear critical, especially in physical hysteretic conditions or conf...

The addition of overset capabilities to the multiphase CFD code, UNCLE-M, allows for a more efficient method to model complex configurations. This technology is displayed by modeling two- and three-dimensional hydrofoils undergoing pitch oscillations for various hydrofoils, cavitation numbers, and pitch frequencies. These simulations include experi...

A Reynolds-Averaged Navier-Stokes computational model of homogeneous multiphase flow is presented. Cavitation driven thrust and torque breakdown over a wide range of advance ratios is modeled for an open propeller. Computational results are presented as a form of validation against water tunnel measured thrust and torque breakdown for the propeller...

A unified computational formulation for homogeneous mixture flows involving multiple phases and multiple species is presented. The formulation is based upon using a generalized equation of state that is valid for arbitrary fluids, including liquids, gases and supercritical fluids. Thermodynamic properties of the mixture are uniformly determined by...

Recent progress in the development and application of homogenous multiphase CFD methods for large-scale gas cavities in liquid flows are presented. The focus of the presentation is on work in n-species transport approaches applied to developed and super-cavitation. Numerical formulation, physical modeling, and applications are included. Numerical i...

A computational model capable of capturing fully compressible multiphase flow including energy conservation is presented. The model is a finite volume form based on the Reynolds Averaged Navier-Stokes Equations and is capable of considering fully general equations of state. The preconditioning matrix is presented and ensures a well conditioned eige...

An unstructured 3D multiphase CFD method has been adapted and applied for the modeling of high Reynolds number external flows with microbubble drag reduction (MDR). An ensemble averaged multi-field two-fluid baseline differential model is employed. Interfacial dynamics models are incorporated to account for drag, lift, virtual mass and dispersion....

A preconditioned, homogeneous, multiphase, Reynolds Averaged Navier-Stokes model with mass transfer is presented. The model is preconditioned in order to obtain good convergence and accuracy regardless of phasic density ratio or flow velocity. Engineering relevant validative unsteady two and three-dimensional results are given. A demonstrative thre...

A time-marching computational fluid dynamics method is developed and applied to the computation of multiphase mixture flows. The model accounts for finite acoustic speeds in the constituent phases, which typically lead to transonic/supersonic flow and associated compressibility phenomena such as shock formation in the mixture region. Preconditionin...

A multi-phase CFD method is used to analyze centrifugal pump performance under developed cavitating conditions. The differential model employed is the homogeneous two-phase Reynolds-Averaged-Navier-Stokes equations, wherein mixture momentum and volume continuity equations are solved along with vapor volume fraction continuity. Mass transfer modelin...

A preconditioned, homogenous, multiphase, Reynolds Averaged Navier-Stokes model with mass transfer is presented. Liquid, vapor, and noncondensable gas phases are included. The model is preconditioned in order to obtain good convergence and accuracy regardless of phasic density ratio or flow velocity. Both incompressible and finite-acoustic-speed mo...

Engineering interest in natural and ventilated cavities about submerged bodies and in turbomachinery has led researchers to study and attempt to model large scale cavitation for decades. Comparatively simple analytical methods have been used widely and successfully to model developed cavitation, since the hydrodynamics of these flows are often domi...

When we discuss high-speed supercavitating bodies, it primarily involves the fully developed supercavitating phase. For many cases the body must transition from fully wetted, through the partially cavitating regime before reaching supercavitation. Therefore, an understanding of all phases of cavitation is necessary. This report presents a summary o...

Unsteady, high Reynolds number validation cases for a multi-phase computational fluid dynamics (CFD) analysis tool have been pursued. The tool, designated UNCLE-M, has a wide range of applicability including flows of naval relevance. This includes supercavitating and cavitating flows, bubbly flows, and water entry flows. Thus far the tool has been...

An implicit algorithm for the computation of viscous two-phase flows is presented in this paper. The baseline differential equation system is the multi-phase Navier–Stokes equations, comprised of the mixture volume, mixture momentum and constituent volume fraction equations. Though further generalization is straightforward, a three-species formulat...

The potential for improved performance of wave rotor cycles through the use of passage height variation is examined. A Quasi-one-dimensional CFD code with experimentally validated loss models is used to determine the flowfield in the wave rotor passages. Results indicate that a carefully chosen passage height profile can produce substantial perform...

A preconditioned, homogenous, multiphase, unsteady Reynolds Averaged Navier-Stokes (URANS) scheme is dynamically coupled to a six-degree-of-freedom (6DOF) rigid body motion model. Details of the numerical and physical modeling associated with the coupled URANS-6DOF code are presented. Results are presented for an application to a notional supercavi...

A three-dimensional, time-accurate, compressible, homogeneous multiphase Navier-Stokes method is applied to modeling developed cavitation flow over a hydrofoil at angle- of-attack. The configuration and cavitation numbers considered give rise to highly unsteady cavitation structures on the suction side of the foil, characterized by large recirculat...

Recent progress in the development and application of homogenous multiphase CFD methods for large-scale gas cavities in liquid flows are presented. The focus of the presentation is on work in n-species transport approaches applied to developed and super-cavitation. Numerical formulation, physical modeling, and applications are included. Numerical i...

Computed single phase and cavitating flow fields are presented for two open propellers and a ducted waterjet. Modeling is performed using a Reynolds-Averaged Navier-Stokes solver with homogenous-multiphase modeling and turbulent simulation capabilities. The open propeller computations include both steady, uniform inflow computations as well as unst...