Laws of Infrared Similitude
NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
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Accurate physical scale models of complex systems are found to be great use in fields as diverse as aerodynamics, fluid mechanics, radar, or nuclear physics. It now appears that the concept of scale modeling may offer distinct advantages to those interested in the study of thermodynamic processes that occur in large physical structure. In this investigation, it is shown from a study of the heat equation and its boundary conditions that physical scale modeling can be used to simulate realistic systems operating in realistic outdoor environments. The thermal properties of the construction materials used in the system under study are allowed to vary with position, this allowing the structure to be divided into a number of compartments. Physical effects which involve heat exchange between the structure and the ocean, or with the atmosphere, are investigated. Both time-dependent and time-independent cases are examined. The scaling laws of thermodynamic similitude which govern the exchange of infrared radiation between any structures and its environment are derived. These scaling laws are then used to obtain a set of dimensionless variables which transform the heat equation and its boundary conditions into manifestly scale invariant form. In this form the heat equation applies to a scale model of arbitrary size.
- Marine Engineering