A new approach for the design of hypersonic scramjet inlets

A new methodology has been developed for the design of hypersonic scramjet inlets using gas dynamic relations. The approach aims to find the optimal inlet geometry which has maximum total pressure recovery at a prescribed design free stream Mach number. The design criteria for inlet is chosen as shock-on-lip condition which ensures maximum capture area and minimum intake length. Designed inlet geometries are simulated using computational fluid dynamics analysis. The effects of 1D, 2D inviscid and viscouseffects on performance of scramjet inlet are reported here. A correction factor in inviscid design is reported for viscouseffects to obtain shock-on-lip condition. A parametric study is carried out for the effect of Mach number at the beginning of isolator for the design of scramjet inlets. Present results show that 2D and viscouseffects are significant on performance of scramjet inlet. Present simulation results are matching very well with the experimental results available from the literature

Two-Phase Analysis of Nanofluid Flow Through A Channel With Heat Transfer

Nano fluids have great significance towards heat transfer applications. It needs to study the nanofluid flows through channels with heat transfer. A steady an incompressible two dimensional forced convection laminar parallel flow through a microchannel and the effect of impinging plane jet flow in a mini-channel using nanofluids studied numerically. In the present study, nanofluid flows through channels are modeled by using a two-phase approach Eulerian-Eulerian model is used. The present study is valid the Reynolds number up to laminar zone. The governing equations solved by using finite volume schemes with first order implicit for time integration. Studied heat transfer characteristics, the parallel flow through micro-channel Re from 109.54 to 285.6, observed heat transfer enhancement with 17.63%, studied the effect of volume fraction in heat transfer with the parallel flow and also studied the effect of base fluids that is the kerosene-based fluid has netted more heat transfer than water-based nanofluid. With the jet flow as the Reynolds, number increases average nusselt number also increases, and also observed the effect of volume fractions on the heat transfer at Re = 200, as the volume fraction from(0.001% to 0.1%) there is an enhancement with 223.23%. Studied the effect of aspect ratios on the heat transfer rate, observed that as the jet inlet to a target surface distance increases average nusselt number decreases. From three different nanofluids (H2O−Al2O3, H2O−Cuo, H2O−T iO2 ) at all volume fractions 0.1%, 1%, 2% the H2O−T iO2 has better enhancement in heat transfer. Observed that the velocity and temperature difference between the liquid phase and solid phases is very small and negligible. The present results are matching well with experimental and numerical results available in the literature

Numerical Study on Buoyancy Induced Flow in Enclosures Connected By Horizontal Vents

The buoyancy-induced flow generated by a heat source such as fire in square enclosures connected by horizontal or ceiling vent has been studied numerically. A two-dimensional laminar and turbulent natural convection flow is investigated with the buoyancy term represented by the Boussinesq approximation. The physical model consists of two enclosures connected by horizontal vent with a finite-size of heat source located centrally on the bottom wall of enclosure. The effects of vent aspect ratio and Rayleigh number on flow field characteristics in enclosures are studied in detail. The results show a significant change in flow behavior for varying vent aspect ratio at a fixed Rayleigh number. A bidirectional and oscillating flow across the vent occurs due to buoyancy. The intensity of thermal plume increases and flow becomes chaotic in enclosures with increase in Rayleigh number. The thermal plume quickly enters to the top enclosure with increase in vent width and decrease in vent thickness

Hybrid RANS/LES of Turbulent forced convection flow over tandem square cylinders

Heat transfer in a turbulent forced convection flow over a tandem square cylinder has been numerically studied at moderate Reynolds numbers. The effects of complex wake interactions behind the cylinder on heat transfer is studied. Turbulence is modelled by Detached Eddy Simulation (DES) with kOmegaSSTDES and SpalartAllmarasDES model available in OpenFOAM solver. The forced convection flow is formulated by two dimensional unsteady incompressible flow by neglecting buoyancy terms. The flow domain dimensions have been chosen such that the blockage ratio is less than 5%. The governing equations are solved numerically by Finite Volume method. Results are reported for different Reynolds numbers by varying spacings between the 2 cylinders from 2D to 5D, varying configuration and varying sizes of cylinders. The velocity and vorticity profiles and average Nusselt number values for both the cylinders are presented. The wake region behind the cylinders varies significantly with spacing between the cylinders affecting the heat transfer characteristics of downstream cylinder. The effect of Reynolds number in heat transfer characteristics is less pronounced in the second cylinder as compared to the first cylinder. The present results are matching well with the available experimental correlations and results available in the literature

Numerical Study on Mixed Convection Flow of Heat Source Modules Mounted On a Horizontal Plate

Mixed convection ow of heat source modules mounted on a horizontal plate has been studied numerically. Present analysis is valid when the buoyancy force effects are small compared to forced convection effects. The mixed convection ow problem is formulated by two- dimensional incompressible ow with the buoyancy term represented by Boussi- nesq approximation. The governing equations are transformed in to an orthogonal trans- formed plane and solved in stream function and vorticity formulation using high accuracy finite difference schemes. Results are reported for single and double heat sources mounted on horizontal plate with and without thickness of the heat source module. Detailed re- sults are reported on the thermal field of heat source modules or electronic components mounted on a horizontal plate and its dependence on physical parameters such as the ex- ternal velocity, energy input, thickness and location of heat source modules etc. Results show that the surface temperature is decreases with the increase of free stream velocity. The surface temperature is decreases with the increase of energy input to the heat source due to buoyancy. The location of the heat source shows significant effect on the surface temperature and thermal field near the heat source. The surface temperature increases with the increase of heat source location from the leading edge of the plate due to increase of thermal boundary layer thickness. The distance between the two heat sources shows a significant effect on thermal field near the heat source modules. The surface temperature is decreases with the increase of thickness of the heat source module due to increase of surface area. The maximum surface temperature and average Nusselt number values are reported for various combinations of Reynolds and Richardson numbers. The reported average Nusselt numbers are matching very well with the experimental results available from the literature

Design and Analysis of Generic Hypersonic Scramjet Inlets

A new methodology has been developed for the design of hypersonic scramjet inlets using gas dynamic relations. The approach aims to find the optimal inlet geometry which has maximum total pressure recovery at a prescribed design free stream Mach number. The design criteria for inlet is chosen as shock-on-lip condition which ensures maximum capture area and minimum intake length. Designed inlet geometries are simulated using CFD analysis. The effects of 1D, 2D, inviscid and viscous effects on performance of scramjet inlet are reported here. A correction factor in inviscid design is reported for viscous effects to obtain shock-on-lip condition. A parametric study is carried out for the effect of throat Mach number in the design of scramjet inlets. Present results show that 2D and viscous effects are significant on performance of scramjet inlet. Performance analysis of scramjets inlets has also been performed. Two planar inlets Mach 10.4 and Mach 7 are considered and the effects of wall cooling, off design and cowl height on the performance of the scramjet inlets are reported. Various performance parameters of scramjet inlets are reported with different operating conditions. Maximum temperatures attained in the inlets are given. Results show that the surface temperature and the cowl height have a significant effect on performance of scramjet inlet. The total pressure recovery coefficient and the spillage losses are reported at different free stream Mach numbers. External flow field analysis is carried out and coefficients of drag and lift are reported here. The Present results are matching well with the experimental results available in the literature

Aspergillus niger for biological control of rhizoctonia solani on coffee seedlings

Aspergillus niger van Tiegh isolated from the rhizosphere of coffee seedlings was found to be antagonistic to the collar rot pathogen, Rhizoctonia solani Kuhn, in vitro and hyperparasitised R. solani completely in dual culture. The mode of hyphal interaction and parasitism of R. solani by A. niger indicated the direct growth of the mycoparasite towards its host and as a consequence the host hypha became vacuolated, collapsed and finally disintegrated. Seed treatment with A. niger spores increased germination. Under glasshouse and field conditions using natural inoculum of R. solani and under artificially infested soils, seed treatment with A. niger reduced the incidence of collar rot disease. A soil incorporation of inoculum was superior to the seed treatment. The possibility of using A. niger as a biocontrol agent against collar rot of coffee is discussed. © 1984 Taylor and Francis Ltd