| Summary: | This paper combines a synthetic jet actuator (SJA) and a leeward porous coating to alter the aerodynamic forces on a cylinder in crossflow at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>e</mi></mrow></semantics></math></inline-formula> = 4.2 × 10<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mn>4</mn></msup></semantics></math></inline-formula>. While SJAs and porous coatings are known to be effective flow control methods in isolation, their combined effect has not been studied. A 2D numerical model was created of a cylinder with a SJA at 90° and 100° leeward porous coating. The model was validated using accompanying water tunnel tests. The combined model was tested for dimensionless frequencies 0.15 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo><</mo><msup><mi>f</mi><mo>+</mo></msup><mo><</mo></mrow></semantics></math></inline-formula> 4 and compared to reference models. For <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>f</mi><mo>+</mo></msup><mo><</mo></mrow></semantics></math></inline-formula> 1, using only the SJA increases the cylinder drag coefficient (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>d</mi></msub></semantics></math></inline-formula>). Combining a porous coating with the SJA in that regime lowers the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>d</mi></msub></semantics></math></inline-formula> values by 15–21%, and causes an overall reduction in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>d</mi></msub></semantics></math></inline-formula> compared to the smooth cylinder baseline case. However, using only the porous coating causes a superior 35% reduction in <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>C</mi><mi>d</mi></msub></semantics></math></inline-formula>. For <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>f</mi><mo>+</mo></msup><mo>></mo></mrow></semantics></math></inline-formula> 1, the combined SJA and porous coating configuration did not differ from the SJA only configuration, achieving the largest drag reduction of 45% at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi>f</mi><mo>+</mo></msup></semantics></math></inline-formula> = 4. The flow control mechanisms of the SJA and porous coating do not combine constructively in this current setup. However, the porous coating is beneficial for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>f</mi><mo>+</mo></msup><mo><</mo></mrow></semantics></math></inline-formula> 1, causing an overall drag reduction even when the active SJA tends to increase drag.
|
|---|