Towards Minimizing Turbulence in Aircraft Inlets

NAGARAJAN RADHAKRISHNAN, Suresh Dhaniyala, Clarkson university

     Abstract Number: 458
     Working Group: Instrumentation and Methods

Abstract
Characterization of properties of stratospheric aerosol particles requires efficient and repeatable aerosol sampling from aircraft platforms. When flow is sampled isokinetically, the flow enters the inlet at high speed and is at a high Reynolds number in the sample tube. Even with the subsequent slowing of the flow, the Reynolds numbers in the sample tube are often high and the flow is turbulent. Flow turbulence can result in significant transport losses for particles, resulting in sampling biases that are difficult to correct theoretically. In this study, we evaluate the low turbulence inlet (LTI) design of Prof. Wilson’s group at Denver University. The LTI, designed for effectively sampling super-micron particles from low-speed aircraft, required boundary layer suction through a porous tube to minimize turbulence in the primary flow. The large size of the inlet, coupled with the need for a large suction pump makes it difficult for the LTI to be deployed with higher altitude aircraft. To improve the LTI design, we evaluated different approaches for boundary layer suction and their impact, flow, and particle transport through the inlet. We will present the different approaches and flow field results, their implications for sampling, and also describe our first design for a compact low-turbulence inlet for use with high-speed aircraft.