Paritosh Mokhasi

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• PhD
• Research Scientist II at University of Mississippi

In the early 1970s, George Carrier and coworkers undertook a modular approach to modelling the internal thermofluid-dynamics of tropical cyclones of tropical-depression-or-greater intensity. A novel, relatively simplistic, approximate analysis of the vortex, idealized as axisymmetric, was carried out in the asymptotic limit of large Reynolds number...

The solution of differential equations using the software package Mathematica is discussed in this paper. We focus on two functions, DSolve and NDSolve, and give various examples of how one can obtain symbolic or numerical results using these functions. An overview of the Wolfram Demonstrations Project (http://demonstrations.wolfram.com) is given,...

In this paper, particle image velocimetry (PIV) results from the recirculation zone of a backward-facing step flow, of which the Reynolds number is 2800 based on bulk velocity upstream of the step and step height (h = 16.5 mm), are used to demonstrate the capability of proper orthogonal decomposition (POD)-based measurement models. Three-component...

Understanding and controlling the dispersion of pollutants and contaminants in urban areas has become a major concern in the last decade. This study addresses the need for a better understanding of the dynamics involved in the flow field around complex geometries and the need for novel techniques to sense and predict its temporal evolution. Experim...

In this paper, particle image velocimetry (PIV) results from a backward-facing step flow, of which Reynolds number is 2800 based on free stream velocity and step height (h = 16.5 mm), are used to demonstrate the capability of proper orthogonal decomposition (POD)-based estimation models. Three-component PIV velocity fields are decomposed into a set...

A fully adaptive mesh-free method based on radial basis functions (RBF) is proposed for numerically solving the Navier- Stokes equations. The scheme is based on the method of lines wherein the spatial derivatives are approximated using a differential quadrature approach. The solution is progressed in time using a fractional step method with pressur...

A new approach to estimating velocity fields from sensor measurements is proposed based on approximating the correlation of the unknown velocity fields with a sample ensemble of snapshots. Proper orthogonal decomposition (POD) is performed on the ensemble to extract the spatial eigenfunctions. If the POD coefficients are known at a certain instance...

Prediction of the spatial and temporal phenomena of wind flow patterns through urban areas is investigated. Typically sparse measurements are used in wind forecasting models for updating and prediction via a method called variational data assimilation. To improve upon this method, an experimental investigation combining various measurement tools (H...

The Lattice Boltzmann method (LBM) is used to simulate turbulent channel flow. Two simulations are performed. One uses high enough grid resolution in order for it to be considered a direct numerical simulation (DNS). LBM in its traditional form is adopted for this simulation. The other simulation uses lower resolution for which the original method...

Focussing on applications to fluid flow phenomena, we are interested in developing dynamical system models that are based on the discrete multivariate time series information only. A method based on radial basis functions and linear multi-step methods is used to construct continuous nonlinear models that approximate the original dynamical system. I...

We are considering the problem of real-time prediction of 3D turbulent velocity fields based on a small number of scalar measurements. The method of proper orthogonal decomposition (POD) allows for the decomposition of an ensemble of velocity fields into a set of spatial basis functions and a set of temporal coefficients. The computation of the tem...

One of the long standing problems of fluid mechanics has been and still is, to obtain the spatio-temporal solution of the velocity field for general boundary conditions. The complexity of the Navier-Stokes equations makes obtaining the solution to general problems intractable except for some very special cases. Under such circumstances, one is left...

In this paper, the problem of approximating velocity fields at future and past times based on information available at the current time is addressed. A novel method called “episodic POD” is described and developed that enables us to achieve our objective. Application of episodic POD to an ensemble of flow data results in a set of spatio-temporal ei...

The problem of approximating velocity fields at future and past times based on information available at the current time is addressed. A novel method called ``episodic POD'' is described that enables us to achieve our objective. Application of episodic POD to an ensemble of flow data results in a set of spatio-temporal eigenfunctions and a set of c...

We are interested in developing dynamical systems models that are based on discrete multivariate time series information only, with application to fluid flow phenomena. A method that uses radial basis functions and linear multi-step methods is developed to construct continuous nonlinear models that approximate the original dynamical system. Informa...

An experimental investigation of the flow around a wall-mounted cube in an experimentally modeled thick atmospheric boundary layer will be presented. Simultaneous Stereoscopic PIV measurements around the cube and pressure measurements on its surface are combined to obtain the 3D velocity field resolved both in space and time using a combination of...

We want to predict 3-D velocity fields in complex geometries with applications to real-time solutions of the contaminant dispersion problem in an urban setting. Proper Orthogonal Decomposition is used to extract a set of optimal basis functions from an ensemble of snapshots. If the temporal coefficients can be computed, then combined with the basis...

The lattice Boltzmann method (LBM) is considered an attractive alternative to conventional CFD methodologies for the numerical simulation of turbulence in complex geometries because it recovers the Navier-Stokes equations and is computationally efficient and easily parallelizable. Additionally, LBM solves a single continuous particle distribution (...

In this talk we will discuss the derivation of evolution equations, which take the form of discrete maps, for the modes of episodic POD. The method of episodic POD is an extension of standard POD that leads to the construction of spatio-temporal POD eigenfunctions called ``episodic modes.'' In contrast to standard POD, this method produces dynamica...

Many classes of turbulent flows, including wall-bounded turbulence, are known to exhibit organized behavior in the form of coherent structures underneath their chaos and nonlinearity. One of the current methods to detect organized flow phenomena is the method of Proper Orthogonal Decomposition (POD). POD enables us to decompose flow fields into a s...

In order to address the direct and inverse problems of contaminant dispersion, the need for complete three-dimensional flow-fields at previous and future time steps is very important. The method of Proper Orthogonal Decomposition (POD) allows us to decompose a 3D flow field into a set of basis functions and temporal coefficients. Recently it was sh...

We are interested in modeling the atmospheric transport of contaminants, in complex geometries as in urban flow problems. One of our goals is to predict contaminant dispersion based on flow and concentration measurements using a minimum number of sensors. The POD method provides a representation of turbulent flow using a minimum amount of informati...

In this paper, we discuss a novel approach to the description of atmospheric flows in urban geometries. Our technique is based on the method of proper orthogonal decomposition POD. We devise a method that enables us to compute the time-varying coefficients of a Karhunen–Loè ve expansion of the urban flow field using knowledge of instantaneous veloc...

We are interested in modeling the transport of contaminants in the atmospheric boundary layer, in complex geometries as in urban flow problems. One of our goals is to predict contaminant dispersion based on flow and concentration measurements using a minimum number of sensors. Since atmospheric flows are almost always turbulent, a direct approach w...