General ram correlations for automobiles



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Texas Tech University


The driving pressure required for the cooling system airflow comes from two sources: the pressure due to the forward motion of the vehicle known as ram pressure, and the radiator fan pressure rise. These internal and external flow fields interact at the cooling air inlets and at the underside of the engine bay. These flow fields are closely related and are considered together in this study. The primary focus of this study is to find general ram pressure correlations for automobiles. The principal test results consist of a set of correlation equations which describe the variation of the ram pressure coefficient with respect to the size and location of the openings, the freestream velocity, and the cooling air flow rate for individual and combinations of openings. These correlations are in a format suitable for use with streamtube cooling system models such as ttu Cool®.