Creating lifting force in liquids via thermal gradients

Qingwen Dai; Jin Yan; Arman Sadeghi; Wei Huang; Xiaolei Wang; M M Khonsari

doi:10.1016/j.jcis.2022.09.002

Creating lifting force in liquids via thermal gradients

J Colloid Interface Sci. 2023 Jan;629(Pt B):245-253. doi: 10.1016/j.jcis.2022.09.002. Epub 2022 Sep 6.

Authors

Qingwen Dai¹, Jin Yan², Arman Sadeghi³, Wei Huang², Xiaolei Wang², M M Khonsari⁴

Affiliations

¹ National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; Institute for Nano- and Microfluidics, Technische Universität Darmstadt, Darmstadt 64287, Germany. Electronic address: daiqingwen@nuaa.edu.cn.
² National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
³ Department of Mechanical Engineering, University of Kurdistan, Sanandaj 66177-15175, Iran.
⁴ Department of Mechanical and Industrial Engineering, Louisiana State University, Baton Rouge, LA 70803, United States. Electronic address: knonsari@lsu.edu.

PMID: 36155919
DOI: 10.1016/j.jcis.2022.09.002

Abstract

In this paper, we explore a concept and present the first experimental evidence to show that it is possible to form a stable liquid film and create lifting force at the interface via thermal gradient to minimize interfacial rubbing of surfaces and the associated wear. The approach is based on manipulating the flow behavior via thermocapillary, which describes how a liquid can be made to flow from warm to cold regions purely by inducing a thermal gradient. We show that liquid bridges between two parallel plates can be manipulated and stabilized under a combined effect of the thermocapillary flow and the Couette flow, which describes the motion of a viscous fluid between two parallel plates in a relative sliding motion. The equilibrium stage is confirmed under different experimental conditions of a thermal gradient, interfacial gap, liquid viscosity, and liquid bridge volume. A strategy is proposed to control liquid motion and create lifting force between two plates. A theoretical model is also presented to illustrate the principle of the equilibrium stage. Creating lifting forces at the interface offers a new thermo-hydrodynamic tool for manipulating liquids behavior. This approach has the potential for controlling liquid motion in mechanical components and nature.

Keywords: Couette flow; Lifting force; Liquid bridge; Thermocapillary flow; Thermohydrodynamic effect.