Experimental assessment of CFD predictions of fascia performance

A numerical and experimental investigation was undertaken to assess the accuracy and sensitivity of a commercial CFD code when predicting the effect of changes to a car fascia on radiator airflow. The Fluent CFD software program was used to model the external and underhood airflow for the front half of a car allowing the mass flow rate of air through the radiator to be calculated. These CFD predictions were compared with experimental measurements of radiator Specific Dissipation (SD) made after CFD predictions were completed. Twenty-two cases were run with five different fascias possessing air inlets that varied in size and shape. The experimental and numerical results obtained showed a 98.4% correlation coefficient with standard deviation of 2.1% on the difference between the techniques and a prediction interval of ±4.2%. Fourteen of the twenty-two cases were ranked correctly giving a Spearman Rank Coefficient of 0.992. In addition, three velocity measurements were made at the back of the radiator using a dynamic probe and showed results that agreed with those predicted numerically to within 5% of the freestream velocity. The cooling performance was found to be sensitive to changes in the geometry of the fascia particularly around the upper cooling inlet.