Journal of Heat Transfer-transactions of The Asme, 2006
A unit-cube geometry model is proposed to characterize the internal structure of porous carbon fo... more A unit-cube geometry model is proposed to characterize the internal structure of porous carbon foam. The unit-cube model is based on interconnected sphere-centered cubes, where the interconnected spheres represent the fluid or void phase. The unit-cube model is used to derive all of the geometric parameters required to calculate the heat transfer and flow through the porous foam. An expression for the effective thermal conductivity is derived based on the unit-cube geometry. Validations show that the conductivity model gives excellent predictions of the effective conductivity as a function of porosity. When combined with existing expressions for the pore-level Nusselt number, the proposed model also yields reasonable predictions of the internal convective heat transfer, but estimates could be improved if a Nusselt number expression for a spherical void phase material were available. Estimates of the fluid pressure drop are shown to be well-described using the Darcy-Forchhiemer law, however, further exploration is required to understand how the permeability and Forchhiemer coefficients vary as a function of porosity and pore diameter.
The holograms considered are formed from opaque or transparent diffracting objects which are cont... more The holograms considered are formed from opaque or transparent diffracting objects which are contained in an aperture illuminated with a coherent, collimated, quasimonochromatic beam of light. It has been shown that the intensity distribution in the near-field of the aperture, but in the far-field of the individual objects which are contained in the aperture, is given by a function whose essential term represents the interference between the Fraunhofer diffraction pattern from the object and the coherent background. The hologram thus formed is referred to as a Fraunhofer or far-field hologram because of the imposed condition. The reconstruction, which is accomplished by placing the recorded hologram in another coherent collimated quasimonochromatic beam and again going to the far-field of the individual objects, yields an intensity which is essentially the original object distribution. In the far-field region of the individual objects for which this result is valid, the reconstruction is seen to be devoid of the evidence of a virtual image. One advantage of this particular method is that the virtual image which appears in the conventional (Fresnel) hologram method creates no problem here since it reduces to a constant for the far-field approximation.
If attention is restricted to the plane of incidence, the location of the interference fringes in... more If attention is restricted to the plane of incidence, the location of the interference fringes in the scattered radiation can be described in the terms shown in the diagram in .
This paper describes a technique by which a large variation phase object may be visualized in an ... more This paper describes a technique by which a large variation phase object may be visualized in an image having an irradiance which is directly proportional to the object phase. An image of the phase object derivative is formed in a coherent optical system and recorded on photographic film. This photograph is used as the input to a second coherent optical system, in which the image is an integral of the input. No limitations are imposed on the maximum object phase, only on its maximum slope. Experimental techniques for implementation of this system are discussed and results shown.
Journal of Heat Transfer-transactions of The Asme, 2006
A unit-cube geometry model is proposed to characterize the internal structure of porous carbon fo... more A unit-cube geometry model is proposed to characterize the internal structure of porous carbon foam. The unit-cube model is based on interconnected sphere-centered cubes, where the interconnected spheres represent the fluid or void phase. The unit-cube model is used to derive all of the geometric parameters required to calculate the heat transfer and flow through the porous foam. An expression for the effective thermal conductivity is derived based on the unit-cube geometry. Validations show that the conductivity model gives excellent predictions of the effective conductivity as a function of porosity. When combined with existing expressions for the pore-level Nusselt number, the proposed model also yields reasonable predictions of the internal convective heat transfer, but estimates could be improved if a Nusselt number expression for a spherical void phase material were available. Estimates of the fluid pressure drop are shown to be well-described using the Darcy-Forchhiemer law, however, further exploration is required to understand how the permeability and Forchhiemer coefficients vary as a function of porosity and pore diameter.
The holograms considered are formed from opaque or transparent diffracting objects which are cont... more The holograms considered are formed from opaque or transparent diffracting objects which are contained in an aperture illuminated with a coherent, collimated, quasimonochromatic beam of light. It has been shown that the intensity distribution in the near-field of the aperture, but in the far-field of the individual objects which are contained in the aperture, is given by a function whose essential term represents the interference between the Fraunhofer diffraction pattern from the object and the coherent background. The hologram thus formed is referred to as a Fraunhofer or far-field hologram because of the imposed condition. The reconstruction, which is accomplished by placing the recorded hologram in another coherent collimated quasimonochromatic beam and again going to the far-field of the individual objects, yields an intensity which is essentially the original object distribution. In the far-field region of the individual objects for which this result is valid, the reconstruction is seen to be devoid of the evidence of a virtual image. One advantage of this particular method is that the virtual image which appears in the conventional (Fresnel) hologram method creates no problem here since it reduces to a constant for the far-field approximation.
If attention is restricted to the plane of incidence, the location of the interference fringes in... more If attention is restricted to the plane of incidence, the location of the interference fringes in the scattered radiation can be described in the terms shown in the diagram in .
This paper describes a technique by which a large variation phase object may be visualized in an ... more This paper describes a technique by which a large variation phase object may be visualized in an image having an irradiance which is directly proportional to the object phase. An image of the phase object derivative is formed in a coherent optical system and recorded on photographic film. This photograph is used as the input to a second coherent optical system, in which the image is an integral of the input. No limitations are imposed on the maximum object phase, only on its maximum slope. Experimental techniques for implementation of this system are discussed and results shown.
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Papers by Brian Thompson