P. A. Aswatha Narayana

Numerical simulation of vortex shedding past a circular cylinder under the influence of buoyancy

Flow past an isolated circular cylinder is numerically simulated, under the influence of aiding and opposing buoyancy. A modified velocity correction procedure is incorporated. Galerkin weighted residual formulation is employed for spatial discretization along with a second-order Runge–Kutta (R–K) time integration scheme. The influence of buoyancy on the Nusselt number, wake structures, temporal lift and drag forces have been studied. At low Reynolds numbers (for, e.g., Re=20–40), buoyancy opposing the flow could trigger vortex shedding. The degeneration of the Karman vortex street into twin vortices is numerically simulated for a heated cylinder. The two zones of vortex shedding and twin vortices are demarcated.

A theoretical model of brick drying as a conjugate problem

Abstract The evaporative drying of a two-dimensional rectangular brick is studied numerically as a conjugate problem. The conservation equations for the solid are obtained using the continuum approach. The Navier–Stokes equations have been employed for obtaining the flow field and the corresponding flow solutions are used for predicting the drying behavior of the brick. The predictions of temperature and moisture content show that the leading edge dries faster compared to other sides of the solid. The full two-dimensional solutions differ considerably from the solutions based on heat and mass transfer through the boundary layers over the top surface. Average heat and mass transfer coefficients appropriate to the conjugate problem have been defined, based on constant temperature and moisture differentials between the solid and the ambient. The corresponding Nusselt and Sherwood number values indicate that analogy does not exist between heat and mass transfer, until the entire brick reaches wet bulb conditions. Free convection effects on drying are also studied for some initial period for low Reynolds number. Due to the influence of buoyant forces imparted by gravity, the overall drying rate has improved.

Finite element simulation of transient laminar flow and heat transfer past an in-line tube bank

Abstract Finite element simulation of transient laminar flow past an in-line tube bank is carried out using a velocity correction procedure. The two-dimensional unsteady Navier–Stokes and energy equations are solved using an explicit and a semi-implicit algorithm for a Reynolds number of 100, a Prandtl number of 0.7, and pitch-to-diameter ratios (PDR) of 1.5 and 2.0. The Galerkin weighted residual formulation is used for the discretization in space. Numerical flow visuals are drawn, showing the time evolution of streamlines. Local and average Nusselt numbers, pressure, and shear stress distributions around the cylinders have also been determined. The results compare well with existing numerical simulations.

Solution of transient laminar natural convection in a square cavity by an explicit finite element scheme

This paper discusses the application of a finite element method based on the first-order projection scheme, which is an extension ofChorins algorithm, to transient laminar natural convection in a square cavity. Results have been presented for a fluid of Prandtl number 0.71 in the Rayleigh number range of 103-106 in terms of the variation of vertical velocity component, nondimensional temperature, and average Nusselt number with time. Various features of the scheme that render it economical in terms of CPU time and storage requirements are discussed. The steady state results have been compared with benchmark solutions, and the agreement appears to be good.

Simulation of laminar confined flow past a circular cylinder with integral wake splitter involving heat transfer

A finite element method is used to study the effect of flow past a circular cylinder with an integral wake splitter. A fractional step algorithm is employed to solve the Navier‐Stokes and Energy equations with a Galerkin weighted residual formulation. The vortex shedding process is simulated and the effect of splitter addition on the time period of shedding is studied at a Reynolds number of 200 and a blockage ratio of 0.25. The effect of splitter and the Strouhal number and heat transfer augmentation per unit pressure drop has been investigated.

Finite element analysis of radial cooled rotating electrical machines

Accurate prediction of temperature distribution in an electrical machine at the design stage is becoming increasingly important. It is essential to know the locations and magnitudes of hot spot temperatures for optimum design of electrical machines. A methodology based on axi‐symmetric finite element formulation has been developed to solve the conduction‐convection problem in radial cooled machines using a new eight noded solid‐fluid coupled element. The axi‐symmetric model adopted is formulated purely from dimensional data, property data and published convective correlations. Steady state temperatures have been determined for 102 kW radial cooled motor at 100 percent and 75 percent loads and are validated with experimental results obtained from heat run tests. Parametric studies have been carried out to study the effect of critical parameters on temperature distribution and for optimising the design.

Performance evaluation of crossflow compact heat exchangers using finite elements

Abstract An analysis of a crossflow compact heat exchanger is carried out using a finite element model. The predictions are in good agreement with analytical solutions available for cases with constant heat transfer coefficients. The analysis is extended to variable heat transfer coefficient cases and the results compared with constant heat transfer coefficient cases. In addition to thermal analysis, the pressure drops are calculated for all cases.

Finite element analysis of mixed convection over in-line tube bundles

Abstract Heat transfer and fluid flow over in-line bundles of cylinders have been numerically simulated. Flow is assurned as incompressible, two-dimensional and laminar. Analysis has been carried out for Reynolds numbers of 50, 100, 150 and pitch to diameter ratios (PDR) of 1.5 and 2.0 with a Prandtl number of 0.71. The effect of Richardson number (Ri = Gr/Re2) on the flow and heat transfer has been investigated for Ri = −1.0, −0.5, 0.0, + 0.5 and + 1.0. Streamlines, temperature contours, average Nusselt numbers, average friction coefficients and pressure distribution around the cylinders are presented. It is observed that there is a considerable effect of buoyancy over tube bundles.

Finite element analysis of shell and tube heat exchanger

Abstract A finite element model to predict temperature distribution in heat exchangers is reported. The model can be effectively used to analyse and design the heat exchangers with complex flow arrangements for which no regular design procedure is available. Illustrations are provided to explain the application of the method for the analysis of shell and tube heat exchangers.

Mixed convection heat transfer past in-line cylinders in a vertical duct

Abstract Heat transfer and fluid flow over a row of in-line cylinders placed between two parallel plates are studied numerically. Solutions of governing equations have been obtained using Eulers explicit algorithm. Numerical results have been obtained for duct watt spacings S/D =1.5, 2.0, and 2.5; Re = 50 and 100; and Pr = 0.7. The effect of Richardson number on die flow and heat transfer has been investigated in the range of Ri = −5.0 to +5.0. Streamlines, temperature contours, local and average Nusselt numbers, pressure, and shear stress distribution around the cylinders are presented. There are considerable effects of buoyancy and the blockage on flow and heat transfer over, the cylinders.