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Kandula, M.

Publications and source records attributed to Kandula, M..

12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Frost Growth and Densification on a Flat Surface in Laminar Flow with Variable Humidity

Experiments are performed concerning frost growth and densification in laminar flow over a flat surface under conditions of constant and variable humidity. The flat plate test specimen is made of aluminum-6031, and has dimensions of 0.3 mx0.3 mx6.35 mm. Results for the first variable humidity case are obtained for a plate temperature of 255.4 K, air velocity of 1.77 m/s, air temperature of 295.1 K, and a relative humidity continuously ranging from 81 to 54%. The second variable humidity test case corresponds to plate temperature of 255.4 K, air velocity of 2.44 m/s, air temperature of 291.8 K, and a relative humidity ranging from 66 to 59%. Results for the constant humidity case are obtained for a plate temperature of 263.7 K, air velocity of 1.7 m/s, air temperature of 295 K, and a relative humidity of 71.6 %. Comparisons of the data with the author's frost model extended to accommodate variable humidity suggest satisfactory agreement between the theory and the data for both constant and variable humidity.

Kandula, M.↗
NASA NTRS2010

Base Flow and Heat Transfer Characteristics of a Four-Nozzle Clustered Rocket Engine: Effect of Nozzle Pressure Ratio

The base pressure and heating characteristics of a four-nozzle clustered rocket configuration is studied numerically with the aid of OVERFLOW Navier-Stokes code. A pressure ratio (chamber pressure to freestream static pressure) range of 990 to 5,920 and a freestream Mach number range of 2.5 to 3.5 are studied. The qualitative trends of decreasing base pressure with increasing pressure ratio and increasing base heat flux with increasing pressure ratio are correctly predicted. However, the predictions for base pressure and base heat flux show deviations from the wind tunnel data. The differences in absolute values between the computation and the data are attributed to factors such as perfect gas (thermally and calorically perfect) assumption, turbulence model inaccuracies in the simulation, and lack of grid adaptation.

Nallasamy, R.↗
NASA NTRS2008

Spectral Attenuation of Sound in Dilute Suspensions with Nonlinear Particle Relaxation

Theoretical studies on the dissipation and dispersion of sound in two-phase suspensions have been briefly reviewed. Previous studies on the sound attenuation in particle-laden flows under Stokesian drag and conduction-controlled heat transfer have been extended to accommodate the nonlinear drag and heat transfer. It has been shown that for large particle-to-fluid density ratio, the particle Reynolds number bears a cubic relationship with Omega Tau(sub d) (where Omega is the circular frequency and Tau(sub d) the Stokesian particle relaxation time). This dependence leads to the existence of a peak value in the linear absorption coefficient occurring at a finite value Omega Tau (sub d). Comparison of the predictions with the test data for the spectral attenuation of sound with water injection in a perfectly expanded supersonic air jet shows a satisfactory trend of the theory accounting for nonlinear particle relaxation processes.

Kandula, M.↗
NASA NTRS2006

Three-Dimensional Thermal Boundary Layer Corrections for Circular Heat Flux Gauges Mounted in a Flat Plate with a Surface Temperature Discontinuity

Three-dimensional Navier-Stokes computational fluid dynamics (CFD) analysis has been performed in an effort to determine thermal boundary layer correction factors for circular convective heat flux gauges (such as Schmidt-Boelter and plug type)mounted flush in a flat plate subjected to a stepwise surface temperature discontinuity. Turbulent flow solutions with temperature-dependent properties are obtained for a free stream Reynolds number of 1E6, and freestream Mach numbers of 2 and 4. The effect of gauge diameter and the plate surface temperature have been investigated. The 3-D CFD results for the heat flux correction factors are compared to quasi-21) results deduced from constant property integral solutions and also 2-D CFD analysis with both constant and variable properties. The role of three-dimensionality and of property variations on the heat flux correction factors has been demonstrated.

Kandula, M.↗
NASA NTRS2002

Corrections for Convective Heat Flux Gauges Subjected to a Surface Temperature Discontinuity

A two-dimensional Navier-Stokes computational fluid dynamics (CFD) analysis has been carried out in an effort to determine the convective heat transfer corrections for circular heat flux gauges subjected to a surface temperature discontinuity. Solutions were obtained at a Reynolds number Of 1 x 10(exp 6) and a Mach number of 4. The CFD results are compared with the existing correlations for the correction factors. In general, the CFD corrections exceed those provided by the correlations. The discrepancy increases with increasing upstream surface temperature, thus indicating the role of property variations, which are not accounted for in the correlations. A quasi-two-dimensional analysis is also performed to treat the cylindrical geometry of the heat flux gauges by area-averaging the computed two-dimensional results from CFD.

Kandula, M.↗
NASA NTRS2002

Simulation of Jet Noise with OVERFLOW CFD Code and Kirchhoff Surface Integral

An acoustic prediction capability for supersonic axisymmetric jets was developed on the basis of OVERFLOW Navier-Stokes CFD (Computational Fluid Dynamics) code of NASA Langley Research Center. Reynolds-averaged turbulent stresses in the flow field are modeled with the aid of Spalart-Allmaras one-equation turbulence model. Appropriate acoustic and outflow boundary conditions were implemented to compute time-dependent acoustic pressure in the nonlinear source-field. Based on the specification of acoustic pressure, its temporal and normal derivatives on the Kirchhoff surface, the near-field and the far-field sound pressure levels are computed via Kirchhoff surface integral, with the Kirchhoff surface chosen to enclose the nonlinear sound source region described by the CFD code. The methods are validated by a comparison of the predictions of sound pressure levels with the available data for an axisymmetric turbulent supersonic (Mach 2) perfectly expanded jet.

Kandula, M.↗
NASA NTRS1993

Numerical simulation of the Space Shuttle Launch Vehicle flowfield with real gas solid rocket plume effects

A numerical simulation of the external ascent flowfield of the Space Shuttle Launch Vehicle (SSLV) was carried out at the freestream Mach number 1.25, the angle of attack -5.1 deg, and the flight Reynolds number 3.25 x 10 exp 6/ft. The simulation is an extension of the solution by Kandula et al. (1991) and incorporates variable gamma effects with a high fidelity grid appropriate for a flight Reynolds number flow solution. Three-dimensional SSLV steady-state simulations with either perfect-gas or variable-gamma-gas Redesigned-Solid-Rocket-Motor (RSRM) plumes are computed on a 14-grid overlapping body-conforming grid system, and the influence of the RSRM exhaust plumes on the SSLV component pressure distributions and integrated loads is examined.

Slotnick, J. P.↗
NASA NTRS1993

Evaluation of Baldwin-Barth turbulence model with thin-layer Navier-Stokes computation of an axisymmetric afterbody-exhaust jet flowfield

Axisymmetric steady flowfield over a steep circular arc afterbody with a choked exhaust jet in a subsonic freestream is numerically investigated using overflow code, developed by NASA Ames. The accuracy of Baldwin-Barth one-equation turbulence model for the computation of separated flow and plume shear layers is assessed by a comparison of predictions with available measurements from NASA Langley. The results show that the Baldwin-Barth turbulence model performs better than the Baldwin-Lomax algebraic model in predicting the surface pressure distribution in the separated flow region of the afterbody. In the jet mixing layer, the Baldwin-Barth model considerably unpredicts the growth of the shear layer, as does the Baldwin-Lomax model. It is shown that the one-equation turbulence model needs improvement for the prediction of separated flow due to smooth adverse pressure gradient, and mixing layer growth.

Kandula, M.↗
NASA NTRS1991

Three-Dimensional Navier-Stokes Simulation of Space Shuttle Main Propulsion 17-inch Disconnect Valves

A steady incompressible three-dimensional viscous flow analysis has been conducted for the Space Shuttle external tank/orbiter propellant feed line disconnect flapper valves with upstream elbows. The Navier-Stokes code, INS3D, is modified to handle interior obstacles and a simple turbulence model. The flow solver is tested for stability and convergence in the presence of interior flappers. An under-relaxation scheme has been incorporated to improve the solution stability. Important flow characteristics such as secondary flows, recirculation, vortex and wake regions, and separated flows are observed. Computed values for forces, moments, and pressure drop are in satisfactory agreement with water flow test data covering a maximum tube Reynolds number of 3.5 million. The predicted hydrodynamical stability of the flappers correlates well with the measurements.

Kandula, M.↗
NASA NTRS1991

Implementation of wall boundary conditions for transpiration in F3D thin-layer Navier-Stokes code

Numerical boundary conditions for mass injection/suction at the wall are incorporated in the thin-layer Navier-Stokes code, F3D. The accuracy of the boundary conditions and the code is assessed by a detailed comparison of the predictions of velocity distributions and skin-friction coefficients with exact similarity solutions for laminar flow over a flat plate with variable blowing/suction, and measurements for turbulent flow past a flat plate with uniform blowing. In laminar flow, F3D predictions for friction coefficient compare well with exact similarity solution with and without suction, but produces large errors at moderate-to-large values of blowing. A slight Mach number dependence of skin-friction coefficient due to blowing in turbulent flow is computed by F3D code. Predicted surface pressures for turbulent flow past an airfoil with mass injection are in qualitative agreement with measurements for a flat plate.

Kandula, M.↗