Journal of Fluids and Structures 97 (2020) 103069 Contents lists available at ScienceDirect Journal of Fluids and Structures journal homepage: www.elsevier.com/locate/jfs Modelling the fluid-flow inside a microchannel under impact loads L. Parras a,∗ , F.J. Galindo-Rosales b a Universidad de Málaga, Escuela de Ingenierías Industriales, C/ Dr. Ortiz Ramos s/n, 29071, Málaga, Spain b Centro de Estudos de Fenómenos de Transporte (CEFT), Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, CP 4200-465 Porto, Portugal article info Article history: Received 19 February 2020 Received in revised form 20 May 2020 Accepted 9 June 2020 Available online xxxx Keywords: Rheinforce cork pads Deformed microchannels Moving mesh abstract This work presents a simple model of the flow generated in microchannels when the upper lid has a vertical deformation that depends on time and space. This model is able to capture the dynamics of the flow generated for two fundamental cases: full displacement of the upper lid and the flow generated by an impactor. The results for these cases have been compared with full 3D simulations with a moving mesh and experiments providing very accurate results. Once the model is validated, it is used for the analysis of the effect of the different parameters that control the flow, and for providing general laws for the non-dimensional energy consumed up to a time t 0 in which the microchannel reaches half of its initial height. Finally, it is demonstrated that the general laws obtained for the non-dimensional energy are fully independent of the closing laws used. © 2020 Elsevier Ltd. All rights reserved. 1. Introduction Squeeze flow is generally used in rheology to characterize the behaviour of complex fluids under biaxial extensional flow. It can be generated in a rotational rheometer equipped with a plate–plate geometry and moving the top plate downward at a controlled velocity, while the bottom plate remains at rest. However, the imposed relative velocity is rather low, of the order of mm/s. The description of its operation can be explained theoretically using Stefan–Reynolds equations (Stefan, 1874; Reynolds, 1886), as it has been done by Dienes and Klemm in Dienes and Klemm (1946) where their theoretical results predicted the experiments with excellent agreement. When the theoretical results do not provide a good agreement, it can be due to the effect of surface tension on their edges or fluid slippage on their surfaces, as discussed in the review article by Engmann et al. (2005). Moreover, it is worthy to note that in real squeeze flow experiments, the fluid may be simultaneously subjected to shear and extensional flow deformations, and consequently, the flow kinematics would only be purely extensional at the stagnation point (Haward et al., 2013). With the advances in microfluidics, the squeeze flow can be exploited at microscale. The external deformation of the microchannels allows them to act as pumps for the transport of liquids or bubbles (Zhang et al., 2015; Aboelkassem, 2019). Insects also use this pumping technique to breathe (Aboelkassem and Staples, 2014), or this flow-vessel interaction can explain the appearance and evolution of aneurysms in small arteries or veins (Virginie Duclaux and Clanet, 2010). Recently, there has been some effort in modelling this kind of flows. Chakraborty et al. (2012) used a Finite Element model with deforming mesh to accurately predict the flow in a microchannel with a deformable wall. Anand et al. (2019) ∗ Corresponding author. E-mail address: lparras@uma.es (L. Parras). https://doi.org/10.1016/j.jfluidstructs.2020.103069 0889-9746/© 2020 Elsevier Ltd. All rights reserved.