Effects of bleed hole size on supersonic boundary layer bleed mass flow rate

Experiments on the influence of distributed injection of helium on the development of the supersonic boundary layer unstable disturbances have been performed. It is revealed, that injection of helium in a certain range of blowing mass flow rate, leads to a certain decrease of spatial amplification rates of natural disturbances.

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Application of Air Microblowing Through a Porous Wall for Skin Friction Reduction on a Flat Plate

Siberian Journal of Physics ◽

10.54362/1818-7919-2010-5-3-38-46 ◽

2010 ◽

Vol 5 (3) ◽

pp. 38-46

Author(s):

Vladimir I. Kornilov ◽

Andrey V. Boiko

Keyword(s):

Boundary Layer ◽

Flat Plate ◽

Skin Friction ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Porous Wall ◽

Friction Reduction ◽

Local Skin ◽

Skin Friction Reduction

The effect of air microblowing through a porous wall on the properties of a turbulent boundary layer formed on a flat plate in an incompressible flow is studied experimentally. The Reynolds number based on the momentum thickness of the boundary layer in front of the porous insert is 3 900. The mass flow rate of the blowing air per unit area was varied within Q = 0−0.0488 кg/s/m2 . A consistent decrease in local skin friction, reaching up to 45−47 %, is observed to occur at the maximal blowing air mass flow rate studied.

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Air Blowing Into Boundary Layer Of A Flat Plate With Length-Dependent Permeability

Siberian Journal of Physics ◽

10.54362/1818-7919-2016-11-3-16-26 ◽

2016 ◽

Vol 11 (3) ◽

pp. 16-26

Author(s):

Vladimir Kornilov ◽

Andrey Boiko ◽

Ivan Kavun ◽

Anatoliy Popkov

Keyword(s):

Boundary Layer ◽

Friction Coefficient ◽

Flat Plate ◽

Skin Friction ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Skin Friction Coefficient ◽

Air Blowing ◽

The Mean

A generalized analysis of the results of numerical and experimental studies of air blowing into a turbulent boundary layer through finely perforated surface consisting of alternating permeable and impermeable sections of varying length providing a sudden change in the flow conditions at the boundaries of these sections is presented. The air blowing coefficient Cb determined by the mass flow rate per unit area of the active perforated sample varied in the range from 0 to 0.008. It is shown that as Cb grows, the maximum reduction in the mean surface skin-friction coefficient CF, which is the value through the permeable area of perforated sample, reaches about 65 %. When keeping the equal mass flow rate Q for all tested combinations, the mean skin-friction coefficient remains constant, independent of geometrical parameters of permeable and impermeable sections. Increasing the length of the last permeable section leads to the growth of relaxation region which is characterized by the reduced skin friction values on the impermeable part of the flat plate.

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Focusing and Defocusing Effects in a Single Liquid-Core/Liquid-Clad Optical Waveguide: An Optical Coupler

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 2 ◽

10.1115/icnmm2011-58006 ◽

2011 ◽

Author(s):

Seyed Reza Mahmoudi

Keyword(s):

Boundary Layer ◽

Mass Flow Rate ◽

Optical Waveguide ◽

Mass Flow ◽

Flow Rate ◽

Wall Temperature ◽

Thermal Boundary Layer ◽

Flow Direction ◽

Liquid Core ◽

Optical Coupler

A single-liquid-core/liquid-clad L2 optical waveguide/coupler is studied numerically. The device consists of a large aspect ratio-microchannel isothermally heated on its both parallel flat walls. Steady state laminar Poiseuille flow of cold water which is introduced to the heated-microchannel forms a stable thermal boundary layer adjacent to the isothermal heated walls. Thermal boundary layer development causes the lateral refractive index gradient across the channel which is required for waveguiding. At a particular mass flow rate for a given wall temperature, the waveguiding occurs. Since the thermal boundary layer, cladding region, is actively tunable through varying both surface temperature and mass flow rate, The waveguiding effect along the channel is highly configurable. We demonstrated that the excitation in the flow direction leads to defocusing of the beam at fundamental TE mode. By reversing the flow direction, the Counter-flow excitation of the waveguide also results in focusing effects. The current waveguide can be exploited as an integrated optical coupler at specific channel wall temperature and mass flow rate.

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Correlation of the mass flow rate in the laminar boundary layer on asphere-cone.

AIAA Journal ◽

10.2514/3.6871 ◽

1973 ◽

Vol 11 (7) ◽

pp. 1044-1046 ◽

Cited By ~ 2

Author(s):

FREDERICK G. BLOTTNER

Keyword(s):

Boundary Layer ◽

Mass Flow Rate ◽

Laminar Boundary Layer ◽

Mass Flow ◽

Flow Rate

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Experimental Investigations of a High Frequency Master-Slave Fluidic Oscillator to Achieve Independent Frequency and Mass Flow Characteristics

Volume 1: Advances in Aerospace Technology ◽

10.1115/imece2016-66782 ◽

2016 ◽

Cited By ~ 2

Author(s):

Valentin Bettrich ◽

Reinhard Niehuis

Keyword(s):

Boundary Layer ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

High Frequency ◽

Turbine Blades ◽

Coupled Oscillator ◽

Fluidic Oscillator ◽

Low Pressure Turbine ◽

Highly Loaded

High frequency fluidic oscillators have been of scientific interest for many decades. Especially over the last couple of years fluidic oscillators became more important for active flow control applications. At the Institute of Jet Propulsion of the University of the German Federal Armed Forces Munich studies on different kinds of flow control methods were carried out on aerodynamically highly loaded low pressure turbine blades. On the basis of these studies, the most efficient way to trigger transition at low Reynolds numbers was found to be with fluidic oscillators at frequencies up to 10 kHz. Still, it is an open issue whether it is most efficient to trigger Tollmien-Schlichting waves, stimulate Kelvin-Helmholtz instabilities or simply induce a frequency independent disturbance in form of a periodic impulse for boundary layer control on aero-dynamically highly loaded low pressure turbine blades. To find an answer to these questions, a high frequency master-slave fluidic oscillator is introduced with an independent frequency and mass flow characteristic. Any frequency from the master oscillator’s characteristic can be chosen and the mass flow rate can be controlled with the slave oscillator. Contrary to concepts with fast switching valves or piezo actuators, this actuator is based on a working principle without the necessity of any moving and life limited parts. Based on experimental results, the characteristics of the master as well as the coupled oscillator are shown. The predictable operation of the coupled device is demonstrated in detail for a constant overall mass flow rate at discrete frequencies of 5 and 6 kHz. In addition, it is also shown that the mass flow can be varied with one master-slave arrangement by a factor of six while keeping the frequency constant at 5 or 6 kHz, respectively. Besides proof of concept these investigations focus on relevant parameters for active boundary layer and transition control. The frequency and velocity spectra of the coupled device are presented for constant frequency and constant mass flow operating points. Based on these results the improvement potential of the coupled oscillator for fundamental research on this topic is discussed.

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Impact of Air Microblowing Through a Permeable Wall on a Turbulent Boundary Layer

Siberian Journal of Physics ◽

10.54362/1818-7919-2011-6-1-77-83 ◽

2011 ◽

Vol 6 (1) ◽

pp. 77-83

Author(s):

Vladimir I. Kornilov ◽

Andrey V. Boiko ◽

Anatoliy N. Popkov

Keyword(s):

Boundary Layer ◽

Skin Friction ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Friction Reduction ◽

Permeable Wall ◽

Sample Length ◽

Local Skin ◽

Boundary Layer Equations

The effectiveness of air microblowing through a permeable wall to reduce a turbulent skin friction over a flat plate in an incompressible flow is studied experimentally and theoretically. The mass flow rate of the blowing air per unit area was varied within Q = 0−0.05 kg 2 m s . A consistent decrease in local skin friction is observed to occur both at the increasing blowing air mass flow rate and along the permeable sample length. No appreciable influence of nondimensional microhole diameter on skin-friction reduction along the length of permeable sample is observed. The experimental results are compared with data of calculation that carried out within the boundary-layer equations

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Effects of Combustor Enclosure Flow Path on Combustor Design

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2020-14127 ◽

2020 ◽

Author(s):

Alejandro M. Briones ◽

Nathan Thomas ◽

Brent A. Rankin

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Three Dimensional ◽

Optimization Procedure ◽

Latin Hypercube Sampling ◽

Small Scale ◽

Hole Size ◽

Practical Applications ◽

Gaussian Kernels

Abstract A design optimization procedure was implemented to resize the holes of a combustor liner for practical applications. A combustor geometry evaluated without an enclosure was to be reformulated within an enclosure. The objective functions of the combustor with enclosure involved targeting the flow splits of the combustor without enclosure. Latin Hypercube Sampling (LHS) design of experiments (DOE) was utilized to obtain at least a pure quadratic response surface (RS). These were computed using Genetic Aggregate (GA). These RS were, in turn, evaluated by a multiple objective genetic algorithm (MOGA) optimizer. The focus of this study was a small-scale cavity-stabilized combustor. Steady, compressible three-dimensional simulations are performed using a multi-phase Realizable k-ε Reynolds-averaged Navier-Stokes (RANS) approach. Combustion-turbulence interaction is modeled with flamelet progress variable (FPV) and β-presumed probability density function (PDF). There are eleven input and output parameters corresponding to the combustor hole sizes and associated mass flow rates. The RS obtained with GA were principally of the Kriging kind (with constant and linear trends and damped sinusoid and Gaussian kernels). A combustor hole mass flow rate was mainly determined by its hole size but was also influenced by the other holes. The combustor flow split non-linearity shows that increasing a hole size increases its mass flow rate, but simultaneously decreases another hole flow rate. This was also verified by sensitivity analysis. Due to this non-linearity, matching flow splits between geometry without and with enclosure is challenging and may not be possible for some situations. Thus, it is concluded that optimization of the combustor geometry without the enclosure is not the best route. Rather, it would be better for the geometry to be optimized with the enclosure included in order to account for flow separation and non-linear influence of the combustor holes on the flow field.

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