• 제목/요약/키워드: Pseudo compressibility

검색결과 25건 처리시간 0.024초

삼차원 정상/비정상 비압축성 유동해석을 위한 비정렬 혼합격자계 기반의 유동해석 코드 개발 (DEVELOPMENT OF AN UNSTRUCTURED HYBRID MESH FLOW SOLVER FOR 3-D STEADY/UNSTEADY INCOMPRESSIBLE FLOW SIMULATIONS)

  • 정문승;권오준
    • 한국전산유체공학회지
    • /
    • 제13권2호
    • /
    • pp.27-41
    • /
    • 2008
  • An unstructured hybrid mesh flow solver has been developed for the simulation of three-dimensional steady and unsteady incompressible flow fields. The incompressible Navier-Stokes equations with an artificial compressibility method were discretized by using a node-based finite-volume method. For the unsteady time-accurate computation, a dual-time stepping method was adopted to satisfy a divergence-free flow field at each physical time step. An implicit time integration method with local time stepping was implemented to accelerate the convergence in the pseudo-time sub-iteration procedure. The one-equation Spalart-Allmaras turbulence model has been adopted to solve high-Reynolds number flow fields. The flow solver was parallelized to minimize the CPU time and to overcome the computational overhead. This method has been applied to calculate steady and unsteady flow fields around submarine configurations and a 3-D infinite cylinder. Validations were made by comparing the predicted results with those of experiments or other numerical results. It was demonstrated that the present method is efficient and robust for the prediction of steady and unsteady incompressible flow fields.

비행선 동체 공력 특성 예측 (Prediction of the Aerodynamic Characteristics of an Airship Hull)

  • 옥호남
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 2001년도 추계 학술대회논문집
    • /
    • pp.76-83
    • /
    • 2001
  • The incompressible Reynolds-averaged Navier-Stokes equations are solved to predict the aerodynamic characteristics of an airship hull. The concept of pseudo-compressibility is employed to couple the pressure field with the velocity field. The upwind differencing method for spatial discretization and a line relaxation scheme for time integration are used. The flowfield around the low drag airship hull of fineness ratio 4 is solved for two Reynolds numbers with a wide range of angle of attack. The effect of Reynolds number and transition position is briefly examined together with the change in aerodynamic coefficients due to a gondola attached to the hull, and the results will be used as basic data for the design of a low drag airship hull.

  • PDF

비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석 (CAVITATION FLOW ANALYSIS OF 2-D HYDROFOIL USING A HOMOGENEOUS MIXTURE MODEL ON UNSTRUCTURED MESHES)

  • 안상준;권오준
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 2011년 춘계학술대회논문집
    • /
    • pp.20-24
    • /
    • 2011
  • In this paper, numerical simulation of cavitation flow for modified NACA66 hydrofoil was made by using the multi-phase RANS equation based on pseudo-compressibility. The Homogeneous mixture model comprised of the mixture continuity, mixture momentum and liquid volume fraction equations was utilized. A vertex-centered finite-volume method was used in conjunction 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing The Spalart-Allmaras one equation model was employed for the closure of turbulence. Reasonable agreements were obtained between the calculation results and the experiment for pressure coefficients on the hydrofoil surface.

  • PDF

2차원 해면효과의 수치계산 (Numerical Simulation of 2-D Wing-In-Ground Effect)

  • ;신명수
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 1998년도 춘계 학술대회논문집
    • /
    • pp.90-98
    • /
    • 1998
  • 본 논문은 2차원 해면효과의 수치계산 결과를 정리하였다. 지면으로부터의 높이변화에 따른 점성유동장을 계산하기 위하여 지배방정식으로는 비압축성 RANS방정식을, 시간에 대하여 서는 음해법으로 프로그램을 구성하였다. 압력항은 가상압축성을 도입 4차 수치확산항을 추가하는 것에 의해 계산하였으며, 높은 레이놀즈수에서의 효과적인 계산을 위해 Baldwin-Lomax 난류 모델을 도입하였다. 해면효과가 없는 무한유중에서의 NACA-0012단면 계산결과를 실험데이터와 비교하는 것에 의해 프로그램의 타당성을 확인하였다. NACA-6409와 두께비 $4.6\%$의 날개에 대하여 해면효과를 고려한 계산을 수행하였다. 높이의 변화에 따라 계산된 무차원계수, 압력 및 속도분포는 해면효과의 특성을 잘 보여주고 있다.

  • PDF

2-방정식 난류모델을 이용한 고양력 익형 주위의 비압축성/압축성 유동장 해석 (Incompressible/Compressible Flow Analysis over High-Lift Airfoils Using Two-Equation Turbulence Models)

  • 김창성;김종암;노오현
    • 한국전산유체공학회지
    • /
    • 제4권1호
    • /
    • pp.53-61
    • /
    • 1999
  • Two-dimensional, unsteady, incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. The compressible code involves a conventional upwind-differenced scheme for the convective terms and LU-SGS scheme for temporal integration. The incompressible code with pseudo-compressibility method also adopts the same schemes as the compressible code. Three two-equation turbulence models are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by predicting the flow around the RAE 2822 transonic airfoil and the NACA 4412 airfoil, respectively. In addition, both the incompressible and compressible code are used to compute the flow over the NLR 7301 airfoil with flap to study the compressible effect near the high-loaded leading edge. The grid systems are efficiently generated using Chimera overlapping grid scheme. Overall, the κ-ω SST model shows closer agreement with experiment results, especially in the prediction of adverse pressure gradient region on the suction surfaces of high-lift airfoils.

  • PDF

2-방정식 난류모델을 이용한 고양력 익형 주위의 비압축성/압축성 유동장 해석 (Incompressible/Compressible Flow Analysis over High-Lift Airfoil Using Two-Equation Turbulence Models)

  • 김창성;김종암;노오현
    • 한국전산유체공학회:학술대회논문집
    • /
    • 한국전산유체공학회 1998년도 추계 학술대회논문집
    • /
    • pp.90-95
    • /
    • 1998
  • The two-dimensional incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. Incompressible code using pseudo-compressibility and dual-time stepping method involves a conventional upwind differencing scheme for the convective terms and LU-SGS scheme for time integration. Compressible code also adopts an FDS scheme and LU-SGS scheme. Several two-equation turbulence models (the standard $k-{\varepsilon}$ model, the $k-{\omega}$ model. and $k-{\omega}$ SST model) are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by computing the flow around the transonic RAE2822 airfoil and the NACA4412 airfoil, respectively. Both the results show a good agreement with experimental surface pressure coefficients and velocity profiles in the boundary layers. Also, the GA(W)-1 single airfoil and the NLR7301 airfoil with a flap are computed using the two-equation turbulence models. The grid systems around two- and three-element airfoil are efficiently generated using Chimera grid scheme, one of the overlapping grid generation methods.

  • PDF

비정렬 격자계에서 균질혼합 모델을 이용한 2차원 수중익형 주위의 캐비테이션 유동 해석 (CAVITATION FLOW SIMULATION FOR A 2-D HYDROFOIL USING A HOMOGENEOUS MIXTURE MODEL ON UNSTRUCTURED MESHES)

  • 안상준;권오준
    • 한국전산유체공학회지
    • /
    • 제17권1호
    • /
    • pp.94-100
    • /
    • 2012
  • In this paper, the cavitating flows around a hydrofoil have been numerically investigated by using a 2-d multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. For this purpose, a vertex-centered finite-volume method was utilized in conjunction with 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing. The Spalart-Allmaras one equation model was employed for the closure of turbulence. A dual-time stepping method and the Gauss-Seidel iteration were used for unsteady time integration. The phase change rate between the liquid and vapor phases was determined by Merkle's cavitation model based on the difference between local and vapor pressure. Steady state calculations were made for the modified NACA66 hydrofoil at several flow conditions. Good agreements were obtained between the present results and the experiment for the pressure coefficient on a hydrofoil surface. Additional calculation was made for cloud cavitation around the hydrofoil. The observation of the vapor structure, such as cavity size and shape, was made, and the flow characteristics around the cavity were analyzed. Good agreements were obtained between the present results and the experiment for the frequency and the Strouhal number of cavity oscillation.

수중 운동체의 거동 및 표면 압력하중 예측에 관한 수치적 연구 (A Computational Study About Behavior of an Underwater Projectile and Prediction of Surficial Pressure Loading)

  • 조성민;권오준
    • 한국군사과학기술학회지
    • /
    • 제20권3호
    • /
    • pp.405-412
    • /
    • 2017
  • In the present study, two phase flows around a projectile vertically launched from an underwater platform have been numerically investigated by using a three dimensional multi-phase RANS flow solver based on pseudo-compressibility and a homogeneous mixture model on unstructured meshes. The relative motion between the platform and projectile was described by six degrees of freedom(6DOF) equations of motion with Euler angles and a chimera technique. The propulsive power of the projectile was modeled as the fluid force acting on the lower surface of the body by the compressed air emitted from the platform. Qualitative analysis was conducted for the time history of vapor volume fraction distributions. Uncorking pressure around the projectile and platform was analyzed to predict impact force acting on the surfaces. The results of 6DOF analysis presented similar tendency with the surficial pressure distributions.

3차원 난류경계층 내에 존재하는 종방향 와동의 유동장 및 열전달 특성에 관한 수치해석(I) - Common Flow Down에 관하여 - (Numerical Analysis on the Flow Field and Heat Transfer Characteristics of Longitudinal Vortices in Turbulent Boundary Layer - On the Common Flow Down -)

  • 양장식
    • 설비공학논문집
    • /
    • 제17권9호
    • /
    • pp.789-798
    • /
    • 2005
  • This paper is a numerical study concerning how the interactions between a pair of the vortices effect flow field and heat transfer. The flow field (common flow down) behind a vortex generator is modeled by the information that is available from studies on a half-delta winglet. Also, the energy equation and the Reynolds-averaged Wavier-Stokes equation for three-dimensional turbulent flows, together with a two-layer turbulence model to resolve the near-wall flow, are solved by the method of AF-ADI. The present results predict that the boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it Is directed away from the wall. Although some discrepancies are observed near the center of the vortex core, the overall performance of the computational model is found to be satisfactory.

압력변화에 따른 ${\beta}$-피콜린과 염화벤조일류의 반응에 대한 연구 (A Study for the Reaction of ${\beta}$-Picoline with p-Substituted Benzoyl Chlorides by Pressure)

  • 김영철;김세경
    • 대한화학회지
    • /
    • 제36권4호
    • /
    • pp.517-522
    • /
    • 1992
  • 10$^{\circ}C$와 20$^{\circ}C$에서 ${\beta}$-피콜린과 치환된 벤조일클로라이드류의 반응을 압력변화에 따라 아세토니트릴용매내에서 전기전도도법으로 연구하였다. 유사 1차속도상수와 2차속도상수로부터 여러 가지 활성화파라미터들(${\Delta}V{\neq}$, ${\Delta}{\beta}{\neq}$, ${\Delta}H{\neq}$, ${\Delta}S{\neq}$ and ${\Delta}G{\neq}$)을 구하고, Hammett ${\rho}$값의 압력의존성을 설명하였다. ${\Delta}V{\neq}$, ${\Delta}{\beta}{\neq}$${\Delta}S{\neq}$ 는 모두 음의 값을 나타내었고, 압력증가에 따라 속도상수와 Hammett ${\rho}$값은 증가하며, 결합형성이 더욱 촉진된 반응메카니즘으로 진행됨을 알 수 있었다.

  • PDF