• Title/Summary/Keyword: blowing or suction

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Characteristics of Wall Pressure Fluctuations in a Turbulent Boundary Layer after Blowing or Suction (흡입/분사가 있는 난류 경계층 내 벽압력 변동의 특성)

  • Kim, Joong-Nyon;Kim, Kyoung-Youn;Sung, Hyung-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.9
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    • pp.1342-1350
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    • 2003
  • A direct numerical simulation of a spatially-developing turbulent boundary layer is performed to examine the characteristics of wall pressure fluctuations after the sudden application of wall blowing or suction. The uniform blowing or suction is given by the wall-normal velocity through a spanwise slot at the wall. The response of wall pressure fluctuations to uniform blowing or suction is analyzed by computing the turbulence statistics and frequency spectra. It is found that wall pressure fluctuations are more affected by blowing than by suction. The large elongated structure of wall pressure fluctuations is observed near the maximum location of $(p_w)_{rms}$ for blowing. The convection velocities for blowing increase with increasing the streamwise location after the slot. For both blowing and suction, the small scale of wall pressure fluctuations reacts in a short downstream distance to the spanwise slot, whereas the large scale recovers slowly in a farther downstream.

Numerical Study of Flow Control of Dynamic Stall Using Continuous Blowing/Suction (정적 Blowing/Suction을 이용한 동실속 유동 제어에 관한 수치적 연구)

  • Choi S. Y.;Kwon O. J.;Kim J. M.
    • 한국전산유체공학회:학술대회논문집
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    • pp.115-119
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    • 2004
  • The effect of a continuous blowing or suction on an oscillating 2-D NACA0012 airfoil was investigated numerically for the dynamic stall control. The influence of control parameter variation was also studied in the view point of aerodynamic characteristics. The result showed that the blowing control kept a higher lift drag ratio before stall angle but the dynamic stall angle was not exceed to without control result. As the slot position was closer to leading edge, the positive control effect becomes greater. The stronger jet and the smaller jet angel made more favorable roles on the control performance. In the cases of the suction, the overall control features were similar to those of the blowing, but dynamic stall angle was increased, i.e. suction was more effective to control dynamic stall. It was also founded that the suction control was showed better control effect as the slot position moves to trail edge within thirty percentage of chord length. In the simulation for the jet strength and the jet angle control, the same tendencies were observed to those of blowing cases.

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Effect of variable viscosity on combined forced and free convection boundary-layer flow over a horizontal plate with blowing or suction

  • Mahmoud, Mostafa A.A.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.11 no.1
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    • pp.57-70
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    • 2007
  • The effects of variable viscosity, blowing or suction on mixed convection flow of a viscous incompressible fluid past a semi-infinite horizontal flat plate aligned parallel to a uniform free stream in the presence of the wall temperature distribution inversely proportional to the square root of the distance from the leading edge have been investigated. The equations governing the flow are transformed into a system of coupled non-linear ordinary differential equations by using similarity variables. The similarity equations have been solved numerically. The effect of the viscosity temperature parameter, the buoyancy parameter and the blowing or suction parameter on the velocity and temperature profiles as well as on the skin-friction coefficient and the Nusselt number are discussed.

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Effect of the Suction Performance by the Air-Curtain Blowing around a Suction Duct (흡입관 주위에 형성된 공기차단막이 흡입성능에 미치는 영향)

  • Cho, Chong-Hyun;Kim, Chae-Sil;Cho, Soo-Yong
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.5
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    • pp.25-32
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    • 2009
  • A study is conducted to improve the suction performance on suction devices which are used to remove polluted air generated by welding or machining process in a spacious working place of industry. Air-curtain is applied around the inlet of suction duct to interrupt the inflow of fresh air from the downstream region where is located opposite to the polluted air source. Two different air-curtain devices, such as a $45^{\circ}$ backward and a fully backward, are adopted. Suction region is experimentally investigated by measuring the suction velocities using a hot-wire anemometer. Contours of the suction velocity are compared with the computed results. The suction condition is selected to 110,000 Reynolds number which is widely used on typical suction devices, and a width of blowing passage for creating the air-curtain is chosen to 9.38% of the suction duct diameter. The experimental results show that the suction performance obtained with the $45^{\circ}$ backward air-curtain was better than that obtained with the fully backward air-curtain. On the suction duct using the $45^{\circ}$ backward air-curtain, the suction region estimated on basis of the 0.4m/sec is improved by 66% at the same input power.

A Study on the Flow Characteristics around a Coanda Control Surface

  • Hong, Seok-Jin;Lee, Seung-Hee
    • Journal of Ship and Ocean Technology
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    • v.8 no.2
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    • pp.13-19
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    • 2004
  • Jet flows applied tangential to a foil surface near the leading and/or trailing edges increase the lift of the foil by delaying the separation also known as the Coanda effects. Many experimental and numerical studies have proven the effectiveness of Coanda effects on circulation control and the effects have been found to be useful in practical application in many aerodynamics fields. Most of the previous works have studied the effects of the jet blowing near the trailing edges and investigated the influence of jet momentum on lift. A few experimental studies, however, focused on the separation bubble that develops near the leading edge and applied jet flow the edge to remove the bubble but only to find decrease in lift. In the present paper, a Coanda foil of 20% thickness ellipse with modified rounded leading and trailing edges was investigated, and the flow around the foil was numerically studied. The blowing around the leading edge only decreased the lift, as the experiments showed, but the suction considerably increased the lift.

Flow Separation Control Effects of Blowing Jet on an Airfoil (블로잉 제트에 의한 에어포일에서의 유동박리 제어효과)

  • Lee, Ki-Young;Chung, Heong-Seok;Cho, Dong-Hyun;Sohn, Myong-Hwan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.12
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    • pp.1059-1066
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    • 2007
  • An experimental study has been conducted to investigate the flow separation control effects of a blowing jet on an elliptic airfoil at a Reynolds number of 7.84×105 based on the chord length. A blowing jet was obtained by pressing a plenum inside the airfoil and ejecting flow out of a thin jet slot that located in leading edge or trailing edge. The experimental results have shown that the blowing jet had an effect of suppressing the flow separation, resulting in the higher suction pressure distribution and higher normal force. The increase in Cn was more pronounced at higher incidence, whereas the effectiveness of the blowing jet reduced at lower incidences. The leading edge pulsating blowing with 90° was the most effective in controlling the flow separation than other types of blowing jet configuration tested in this research. Moreover, when the pulsating blowing was applied, the stall angle was postponed about 2°-3°. The continuous and pulsating blowing jet is a direct and effective flow separation control for improving the aerodynamic characteristics and performances of airfoil.

EXAMPLES OF REDUCED ORDER MODELLING FOR A 3D BACKWARD FACING STEP FLOW USING POD TECHNIQUE (POD를 사용한 3차원 후향계단 유동장 분석 예제)

  • Lee, K.S.;Lee, E.S.
    • 한국전산유체공학회:학술대회논문집
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    • pp.40-42
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    • 2010
  • Unsteady CFD results of the backward facing step (BFS) flow field is reconstructed by the low-dimenstional modes using the POD (Proper Orthogonal Decomposition) technique. Flow responses to the blowing or suction with various frequencies and amplitudes applied at the edge of the BFS can also be analysed using the same technique. The present technique can be effectively applied to the feedback flow control device.

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Synthesis and Shape Control of Calcium Carbonate Fine Powders by Liquid-Gas Reaction Method (액상-기상 반응법에 의한 탄산칼슘 미분말의 합성과 형상제어)

  • 민경소;최상흘
    • Journal of the Korean Ceramic Society
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    • v.28 no.3
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    • pp.205-214
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    • 1991
  • Calcium carbonate fine powders were synthesized by blowing CO2 gas in CaO or Ca(OH)2 suspension, and the shapes of powders obtained were examined for each synthetic condition. When water was used as a solvent, ultrafine calcite powders with the average size of∼0.03$\mu\textrm{m}$ were obtained. When synthesized using methanol as a solvent, amorphous phase and spherical vaterite phase were obtained by suction filtering and non-filtering, respectively. Reaction did not occured in ethanol medium, but spherical vaterite phase was obtained by adding ethylene glycol in ethanol.

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Aeration Factor Used To Design The Container Type of Biopile Systems for Small-Scale Petroleum-Contaminated Soil Projects

  • Jung, Hyun-Gyu
    • Korean Journal of Soil Science and Fertilizer
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    • v.44 no.2
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    • pp.316-319
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    • 2011
  • Biopiles which offer the potential for cost-effective treatment of contaminated soils are above-ground, engineered systems that use oxygen to stimulate the growth and reproduction of aerobic bacteria for degradation of the petroleum constituents adsorbed to soil in excavated soils. This technology involves heaping contaminated soils into piles and stimulating aerobic microbial activity within the soils through the aeration and/or addition of minerals, nutrients, and moisture. Inside the biopile, microbially mediated reactions by blowing or extracting air through the pipes can enhance degradation of the organic contaminants. The influence of a aeration system on the biopile performance was investigated. Air pressure made to compare the efficiency of suction in the pipes showed that there were slightly significant difference between the two piles in the total amount of TPH biodegradation. The normalised degradation rate was, however, considerably higher in the aeration system than in the normal system without aeration, suggesting that the vertical venting method may have improved the efficiency of the biological reactions in the pile.

Flow Analyses around the Battery Pack for a NEV (전기자동차용 배터리 팩 주위의 유동장 해석)

  • Kim, H.S.;Han, B.Y.;Park, H.K.
    • 한국전산유체공학회:학술대회논문집
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    • pp.135-140
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    • 2011
  • The battery pack, a main component of NEV(Neighborhood Electric Vehicle), needs cooling system when it is charging or discharging to prevent the degradation of the battery charging efficiency. The purpose of this study is to analyse the effects of cooling methods, changing positions of inlet and outlet and changing area ratios of inlet and outlet. It has been observed that in the point of uniform cooling suction from the exit side is more efficient than blowing from the inlet. And there is a suitable inlet/outlet area ratio in maximizing the mass flow rate. The numerical analyse using a commercial code STAR-CCM+ version 4.02 were used for the study.

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