Home  About us  Contact
 

Rectangular Cavity (rectangular + cavity)

Distribution by Scientific Domains
Engineering100%

Selected Abstracts

Internal gravity wave resonance of thermal convection fields in rectangular cavities with heat-flux vibration (effects of aspect ratio on the fields)

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2007
Shota Matsumura
Abstract In this paper the thermal convection field and its resonance phenomena in a rectangular cavity with heat-flux vibration are numerically examined and the results are compared with those of a square cavity. As in the case of ,=1, the critical angular velocity at which the relative amplitude of the midplane Nusselt number ,m has a local maximum agrees very well with the resonance angular velocity of the internal gravity wave ,r, estimated by the theoretical equation proposed by Thorpe, even when the aspect ratio is ,=5 and the Prandtl number is Pr=0.71 for a range of the Rayleigh number Ra. However, ,m has two local maxima for a larger Ra, which is peculiar to the case of larger ,. The time variation of sub-components of the fluctuating component of the midplane Nusselt number shows that the phase at the maximum value of ,m agrees well with that of the sub-component of velocity for the first resonance angular velocity ,r. For the other angular velocity ,r2, the phase of ,m agrees with that of the sub-component of temperature. Moreover, we found that the boundary angular velocity ,0 between the first two of the five , regions, which classify the thermal convection fields against ,, can be expressed by a function of ,, Ra, and Pr and that ,m is independent of , and Ra for a relatively wide range of ,/,0. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(3): 158, 171, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20149 [source]

Toward accurate hybrid prediction techniques for cavity flow noise applications

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009
W. De Roeck
Abstract A large variety of hybrid computational aeroacoustics (CAA) approaches exist differing from each other in the way the source region is modeled, in the way the equations are used to compute the propagation of acoustic waves in a non-quiescent medium, and in the way the coupling between source and acoustic propagation regions is made. This paper makes a comparison between some commonly used numerical methods for aeroacoustic applications. The aerodynamically generated tonal noise by a flow over a 2D rectangular cavity is investigated. Two different cavities are studied. In the first cavity (L/D=4, M=0.5), the sound field is dominated by the cavity wake mode and its higher harmonics, originating from a periodical vortex shedding at the cavity leading edge. In the second cavity (L/D=2, M=0.6), shear-layer modes, due to flow-acoustic interaction phenomena, generate the major components in the noise spectrum. Source domain modeling is carried out using a second-order finite-volume large eddy simulation. Propagation equations, taking into account convection and refraction effects, are solved using high-order finite-difference schemes for the linearized Euler equations and the acoustic perturbation equations. Both schemes are compared with each other for various coupling methods between source region and acoustic region. Conventional acoustic analogies and Kirchhoff methods are rewritten for the various propagation equations and used to obtain near-field acoustic results. The accuracy of the various coupling methods in identifying the noise-generating mechanisms is evaluated. In this way, this paper provides more insight into the practical use of various hybrid CAA techniques to predict the aerodynamically generated sound field by a flow over rectangular cavities. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Web based laboratory in electromagnetic compatibility using a Java applet

COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 4 2006
S. K. Goudos
Abstract A web based virtual laboratory in electromagnetic compatibility using a Java applet is presented. The Java applet makes use of Green's functions calculations inside a rectangular cavity. The induced electric fields and surface currents on cavity walls are calculated and visualized in a user-friendly manner. Various source configurations are examined. A number of laboratory exercises using the applet is given. © 2006 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 269,280, 2006; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20087 [source]

Internal gravity wave resonance of thermal convection fields in rectangular cavities with heat-flux vibration (effects of aspect ratio on the fields)

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2007
Shota Matsumura
Abstract In this paper the thermal convection field and its resonance phenomena in a rectangular cavity with heat-flux vibration are numerically examined and the results are compared with those of a square cavity. As in the case of ,=1, the critical angular velocity at which the relative amplitude of the midplane Nusselt number ,m has a local maximum agrees very well with the resonance angular velocity of the internal gravity wave ,r, estimated by the theoretical equation proposed by Thorpe, even when the aspect ratio is ,=5 and the Prandtl number is Pr=0.71 for a range of the Rayleigh number Ra. However, ,m has two local maxima for a larger Ra, which is peculiar to the case of larger ,. The time variation of sub-components of the fluctuating component of the midplane Nusselt number shows that the phase at the maximum value of ,m agrees well with that of the sub-component of velocity for the first resonance angular velocity ,r. For the other angular velocity ,r2, the phase of ,m agrees with that of the sub-component of temperature. Moreover, we found that the boundary angular velocity ,0 between the first two of the five , regions, which classify the thermal convection fields against ,, can be expressed by a function of ,, Ra, and Pr and that ,m is independent of , and Ra for a relatively wide range of ,/,0. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(3): 158, 171, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20149 [source]

Toward accurate hybrid prediction techniques for cavity flow noise applications

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009
W. De Roeck
Abstract A large variety of hybrid computational aeroacoustics (CAA) approaches exist differing from each other in the way the source region is modeled, in the way the equations are used to compute the propagation of acoustic waves in a non-quiescent medium, and in the way the coupling between source and acoustic propagation regions is made. This paper makes a comparison between some commonly used numerical methods for aeroacoustic applications. The aerodynamically generated tonal noise by a flow over a 2D rectangular cavity is investigated. Two different cavities are studied. In the first cavity (L/D=4, M=0.5), the sound field is dominated by the cavity wake mode and its higher harmonics, originating from a periodical vortex shedding at the cavity leading edge. In the second cavity (L/D=2, M=0.6), shear-layer modes, due to flow-acoustic interaction phenomena, generate the major components in the noise spectrum. Source domain modeling is carried out using a second-order finite-volume large eddy simulation. Propagation equations, taking into account convection and refraction effects, are solved using high-order finite-difference schemes for the linearized Euler equations and the acoustic perturbation equations. Both schemes are compared with each other for various coupling methods between source region and acoustic region. Conventional acoustic analogies and Kirchhoff methods are rewritten for the various propagation equations and used to obtain near-field acoustic results. The accuracy of the various coupling methods in identifying the noise-generating mechanisms is evaluated. In this way, this paper provides more insight into the practical use of various hybrid CAA techniques to predict the aerodynamically generated sound field by a flow over rectangular cavities. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Stability and slightly supercritical oscillatory regimes of natural convection in a 8:1 cavity: solution of the benchmark problem by a global Galerkin method

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2004
Alexander Yu.
Abstract The global Galerkin method is applied to the benchmark problem that considers an oscillatory regime of convection of air in a tall two-dimensional rectangular cavity. The three most unstable modes of the linearized system of the Boussinesq equations are studied. The converged values of the critical Rayleigh numbers together with the corresponding oscillation frequencies are calculated for each mode. The oscillatory flow regimes corresponding to each of the three modes are approximated asymptotically. No direct time integration is applied. Good agreement with the previously published results obtained by solution of the time-dependent Boussinesq equations is reported. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Resonance shifting and plane impedance calculations for a rectangular cavity in printed circuit board using closed form solutions

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2009
K. Cantrell
Abstract A method for arbitrarily shifting the dominant mode frequency of a rectangular cavity in printed circuit boards (PCBs) is presented. Standard closed-form and analytic solutions are used to determine the frequency, quality factor, and impedance of the cavity. Calculations are compared with 3D full wave finite element method (FEM) solutions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 452,455, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24080 [source]