ANALYSIS OF THE USE OF SPOILER ONE LEVEL AND TWO LEVELS IN CONDITIONS OF STEADY AGAINST THE DRAG AND LIFT COEFFICIENTS ON A SEDAN TYPE CAR BY USING CFD (COMPUTATIONAL FLUID DYNAMIC)

Abstract

This research was simulation analyzing the condition of steady flow in around of body car made and analized computly using CFD program (Computational Fluid Dynamic). The model used was Sedan car designed with different rear end body by adding spoiler. Analyzing in this research was done by using Software 18.2–CFD Student Version. Design of the three models were compared to find out the difference in magnitude of Coefficient of Drag, Coefficient of Lift, pressure distribution, velocity distribution, and behavioral character of flow around the rear end of car in the condition of steady flow. Model was made in appropriate scale with model of Honda city 2008 sedan car. Observation was made to look at the behavior of fluida flows both in front and back the car in different fluid speed ranges in steady condition.

The simulation results obtained from packet CFD on each condition were; model without spoiler, model with 1 level spoiler, and model with 2 level spoiler. Where this simulation showed that CD and CL were decrease. One of the example was at speed 40km/hour obtained the coefficient of drag (CD) of 0.31061, 0.28603, and 0.2054, it proved that 1 level spoiler could reduce the value of drag coefficient about 7.9135% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of drag coefficient about 33.8592% without spoiler. For the coefficient of lift (CL) on each model was -0.38487, -0.54624, and -0.62097 proved that spoiler 1 level could reduce the value of lift coeffient about 41.92845% of the sedan car without spoiler, while the car with 2 level spoiler could reduce the value of lift coefficient about 61.35984% without spoiler. On the result of pressure distrubution and relative velocity give little affect to the upper and lower surface where this was indicated by almost no color difference contours. Then, if it was indicated from streamline and the formation of vortex, there was a significant difference so that it was very influential on the size of CD and CL occoured. By changing geometric proved that the spoiler car 1 and 2 level were more aerodynamic than the car without spoiler.