Monte Carlo computation of rarefied supersonic flow into a pitot probe

Kannenberg, Keith; Boyd, Iain D.

doi:10.2514/3.13025

Cited by 15 publications

(2 citation statements)

References 8 publications

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“…Where this is the case, the pressure loss across the normal shock is less than that predicted by the Rayleigh relation. 25,27 In order to take into account possible measurement errors due to rarefaction and non-equilibrium effects on the probe, a correction was considered. The correction depends on the Reynolds number of the sting probe Re sting , which is defined as Re sting = ρD sting U/ √ µ.…”

Section: Design and Experimental Setupmentioning

confidence: 99%

Rarefied flow expansion in linear aerospikes

Giovannini

Abhari

2015

Physics of Fluids

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The formation of the kinetic boundary layer (KBL) on diverging surfaces is studied experimentally and computationally. The diverging surfaces are chosen to follow profiles commonly used for linear aerospikes, in order to study the KBL formation in an ideal and two-dimensional flow expansion bounded only on one side. Experiments with different operating conditions at low Re number (from 132 to 2826) and in the transition regime (Kn number from 6.4 to 0.42) are used to evaluate the thickness of the KBL. The ambient pressure, the ratio between the stagnation and surface temperature, the roughness and the shape of the surface are parametrically varied maintaining the same pressure ratio between the total and the ambient pressures. Simulations are validated and used to study the influence of gas-surface interaction on formation of the KBL and to quantify the non-equilibrium state of the flow field. It is shown that the topography of the surface does not influence the growth of the KBL, but the flow can be tailored by modifying the shape of the surface. Using the experimental and computational data, a phenomenological model is developed to predict growth of the KBL. The thickness of the KBL is proportional to the length along the surface and to the mean free path. Furthermore, the ratio between the mean free path on the surface and the thickness of the KBL is found to be an invariant for the diverging surfaces modified through linear corrections. In the aerospike system, the KBL reduces the thrust by 35% and the proposed corrected geometry increases the real thrust by 20%.

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Section: Design and Experimental Setupmentioning

confidence: 99%

Rarefied flow expansion in linear aerospikes

Giovannini

Abhari

2015

Physics of Fluids

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“…Rarefied supersonic flows through channels and tubes have been studied analytically 5 and computationally using DSMC due to its importance in many technical applications. [6][7][8] For microchannels the two-dimensional ͑2D͒ DSMC simulations so far have addressed Knudsen numbers in the range of 0.0046-0.744 covering the slip and transitional regimes for nitrogen and helium gases. [9][10][11][12][13] Microchan-nels considered in these investigations have fully diffuse walls and heights in the range of 0.1-2.4 m with aspect ratios ͑ARs͒ in the range of 2.5-5.…”

Section: A Dsmc Computation Of Rarefied Supersonic Microflowsmentioning

confidence: 99%

Investigation of rarefied supersonic flows into rectangular nanochannels using a three-dimensional direct simulation Monte Carlo method

2010

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The rarefied flow of nitrogen with speed ratio ͑mean speed over most probable speed͒ of S =2,5,10, pressure of 10.132 kPa into rectangular nanochannels with height of 100, 500, and 1000 nm is investigated using a three-dimensional, unstructured, direct simulation Monte Carlo method. The parametric computational investigation considers rarefaction effects with Knudsen number Kn= 0.481, 0.962, 4.81, geometric effects with nanochannel aspect ratios of ͑L / H͒ from AR=1,10,100, and back-pressure effects with imposed pressures from 0 to 200 kPa. The computational domain features a buffer region upstream of the inlet and the nanochannel walls are assumed to be diffusively reflecting at the free stream temperature of 273 K. The flow analysis is based on the phase space distributions while macroscopic flow variables sampled in cells along the centerline are used to corroborate the microscopic analysis. The phase-space distributions show the formation of a disturbance region ahead of the inlet due to slow particles backstreaming through the inlet and the formation of a density enhancement with its maximum inside the nanochannel. Velocity phase-space distributions show a low-speed particle population generated inside the nanochannel due to wall collisions which is superimposed with the free stream high-speed population. The mean velocity decreases, while the number density increases in the buffer region. The translational temperature increases in the buffer region and reaches its maximum near the inlet. For AR = 10, 100 nanochannels the gas reaches near equilibrium with the wall temperature. The heat transfer rate is largest near the inlet region where nonequilibrium effects are dominant. For Kn = 0.481, 0.962, 4.81, vacuum back pressure, and AR= 1, the nanoflow is supersonic throughout the nanochannel, while for AR= 10, 100, the nanoflow is subsonic at the inlet and becomes sonic at the outlet. For Kn= 0.962, AR= 1, and imposed back pressure of 120 and 200 kPa, the nanoflow becomes subsonic at the outlet. For Kn= 0.962 and AR= 10, the outlet pressure nearly matches the imposed back pressure with the nanoflow becoming sonic at 40 kPa and subsonic at 100 kPa. Heat transfer rates at the inlet and mass flow rates at the outlet are in good agreement with those obtained from theoretical free-molecular models. The flows in these nanochannels share qualitatively characteristics found in microflows and continuum compressible flows in channels with friction and heat loss.

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Gas–surface interaction effects on the flowfield structure of a high speed microchannel flow

Sebastião

Santos

2013

Applied Thermal Engineering

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Abstract. This work describes a computational study on supersonic flow in a microchannel composed of two parallel plates. Effects of incomplete surface accommodation on the flowfield structure have been investigated by employing the Direct Simulation Monte Carlo (DSMC) method in combination with the Cercignani-Lampis-Lord (CLL) gas-surface interaction model. The aim of this work is to investigate the disturbance developments due to differences in the accommodation coefficients on the lower and upper surfaces of the microchannel. The results presented highlight the sensitivity of the primary properties to changes on the gas-surface accommodation coefficients. It is found that accommodation coefficients have different influence on velocity, density, pressure and temperature for the conditions investigated.

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Monte Carlo computation of rarefied supersonic flow into a pitot probe

Cited by 15 publications

References 8 publications

Rarefied flow expansion in linear aerospikes

Rarefied flow expansion in linear aerospikes

Investigation of rarefied supersonic flows into rectangular nanochannels using a three-dimensional direct simulation Monte Carlo method

Gas–surface interaction effects on the flowfield structure of a high speed microchannel flow

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