An integrated study of parallel valveless micropumps

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.We describe an analytical, computational and experimental study of parallel valveless micropumps. A one dimensional model of a parallel micropump is presented and compared with available experimental data. The model confirms the linear decrease of the volume flux with pressure rise which is consistent with the experiments. The computational study showed a similar linear decrease but highlighted the effect of turbulence closures on the rectified mean flow, with the experimental data sitting between the turbulent and laminar closure regimes. The experimental study confirmed the importance of the displacement distance of fluid through the nozzle compared to nozzle length in the setting whether the flow regime is streaming or rectified. General conclusions are made about how to improve the pumping efficiency of micropumps.This study is supported by the Dorothy Hodgkin Postgraduate Award (DHPA) of the Engineering and Physical Sciences Research Council (EPSRC) of United Kingdom and Ebara Research Co. Ltd of Japan

Analysis and design optimization of an integrated micropump-micromixer operated for bio-MEMS applications

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.A generic microfluidic system composed by two single chamber valveless micropumps connected to a simple T-type channel intersection is examined numerically. The characteristics of a feasible valveless micropump have been used in the design, where efficient mixing is produced due to the pulsating flow generated by the micropumps. The advantages of using time pulsing inlet flows for enhancing mixing in channels have been harnessed through the activation of intrinsic characteristics of the pumps required to achieve the periodic flows. A parametric study is carried out on this microfluidic system using Computational Fluids Dynamics (CFD)on a design space defined by a Design-of-Experiments (DOE) technique. The frequency f and the phase difference f of the periodic fluid velocities (operation parameters) and the angle q formed by the inlet channels at the intersection (geometric parameter) are used as design parameters, whereas mixing quality, pressure drop and maximum shear strain rate in the channel are the performance parameters. The study identifies design features for which the pressure drop and shear strain are reduced whereas the mixing quality is increased. The proposed microfluidic system achieves high mixing quality with performance parameters that enable manipulation of biological fluids in microchannels

High-Strouhal-number pulsatile flow in a curved pipe

The high-Strouhal-number pulsatile flow in a curved pipe is studied numerically. A general force analysis is developed for the bend force, where the new contribution from flow acceleration is identified and analysed. The mechanisms of secondary flow production are studied by extending Hawthorne's (Proc. R. Soc. Lond. A, vol. 206, issue 1086, 1951, pp. 374–387) model to account for viscous effects and applied to assess the distinct contributions from an inviscid stretching and no-slip condition. A detailed comparison is made between the numerical simulations and models for a pipe flow characterised by a volume flux Q=UbA|sinΩpt| (where Ub is the maximum bulk velocity, Ωp is the angular frequency and A is the pipe cross-sectional area). For high-Reynolds-number (Reb) and high-Strouhal-number (St), the bend force predictions are in good agreement with the numerical results over a wide range of bend curvature (Rc/D; where Rc is the bend radius of curvature and D is the pipe diameter) owing to the influence of the streamwise flow acceleration on the pressure field. At high-St, the streamwise vorticity (secondary flow) distribution is steady and close to the low-St case, which is explained using a linear secondary flow model

Acoustics and vibrations in a complex piping network with pump startup–shutdown transients

Pump dynamic operational conditions result in extreme transient events that can enhance the response of piping networks. The predominant transients during rapid startup and shutdown are mainly studied for centrifugal pumps and are scarce for reciprocating pumps. Our study extends the conventional steady-state analysis to include the effect of reciprocating pump dynamic loading on pulsatile flow-induced acoustics and vibrations in a complex piping network. The forced response resulting from acoustical–structural coupling is assessed by utilising the one-dimensional multiphysics piping acoustic model and beam structural model. The network responses to pulsatile flows during dynamic pump loading (rapid start-up-shutdown events) are compared to the responses due to pulsatile flows during steady-state pump loading. With pump startup–shutdowns operations accompanied by pulsatile flows, the network response is the result of the combination of the transient and steady-state characteristics of plane acoustic waves and structural vibrations. The dynamic pump loading excites the fundamental, low-frequency acoustic eigenmode that causes transient loading of pipeline similar to reservoir–pipe–valve (RPV) systems

Evolving Sims's creatures for bipedal gait

“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”In this paper we describe the design of an approach to evolve Sims's creatures with morphology and behaviour similar to biped animals. Our hypothesis is that biases in morphology that encourage limb specialisation, combined with rewards for successful locomotion and carrying at the same time and realistic, physics-based penalties for falling in fitness function, would lead to creatures capable of bipedal locomotion. We present experimental results demonstrating successful evolution of biped morphology and stepping gait

An efficient passive planar micromixer with fin-shaped baffles in the tee channel for wide Reynolds number flow range

A new design of a planar passive T-micromixer with fin-shaped baffles in the mixing channel is presented. The mixing efficiency and the level of pressure loss in the channel have been investigated by numerical simulations in the range of Reynolds number (Re) 1 to 50. A Mixing index (Mi) has been defined to quantify the mixing efficiency, which results over 85% at both ends of the Re range, what demonstrates the micromixer can enhance mixing using the mechanisms of diffusion (lower Re) and convection (higher Re). Three geometric dimensions: radius of baffle, baffles pitch and height of the channel define the design parameters, and the mixing index and pressure loss are the performance parameters used to optimize the micromixer geometry with a multi-criteria optimization method. The Pareto front of designs with the optimum trade-offs, maximum mixing index with minimum pressure loss, is obtained. Experiments for qualitative and quantitative validation have been implemented.Peer reviewe

Investigation of Double-Chamber Series Valveless Micropump : An Analytical Approach

We describe an analytical study of the characteristics of a double-chamber series valveless micropump using a one-dimensional non-linear model. We derive a closed-form expression for relationship between the mean volume flux, pressure difference and measurable characteristics of the pump. To first order, the results show the linear decrease of the volume flux with the pressure difference, which is consistent with other types of valveless pump configurations

Optimization of diffuser/nozzle elements for rectification valveless micropumps

Paper no. FEDSM-ICNMM2010-30856There has been a growing interest in understanding the flow behaviour inside diffuser/nozzle elements in order to identify performance characteristics of these elements for micropump applications. Flat-walled diffuser/nozzle element is the most commonly used type for valveless micropump applications due to its ease of fabrication and compact design. In this paper, we study generic flat-walled diffuser/nozzle elements and apply optimization techniques to explore how the pumping efficiency can be improved by changing geometry to provide higher rectification efficiency and lower pressure drop in rectification valveless micropumps. The primary motivation for this study is to evaluate the performance of flat-walled diffuser/nozzle elements based on geometry variations under several Reynolds numbers (Re). In this study we employ a design methodology for diffuser/nozzle elements that incorporates computational fluid dynamics (CFD) within an optimization methodology. To start the process a series of geometric parameters are selected including element neck width, depth, divergence angle, and entrance fillet radius. Then, the pressure drop and rectification property of an element are calculated as performance parameters, i.e., by varying the geometry it is desirable to maximise pressure rise and the rectification property of the element. Design of experiments (DOE) is employed to generate the experimental table which corresponds to different geometries representing the design space. These limited numbers of geometries generated by DOE are evaluated by using CFD to obtain corresponding performance parameters. By preparing all the design and performance parameters, Surrogate model (SM) technique is applied to obtain the relationship (approximation function) between design and performance parameters. Eventually, based on the developed approximation functions or response surfaces, a multi-objective genetic algorithm (MOGA) is employed to maximise pressure rise and rectification property of diffuser/nozzle element. This design methodology is a very powerful tool to design and optimise flat-walled diffuser/nozzle elements for micropump applications and can speed up the micropump design process significantly

Acoustics interaction in a complex piping network with multiple pulsatile sources

The interactions between multiple pulsatile sources and the acoustic eigenmodes are analysed to elucidate the influence of source characteristics and contrasting phase differences on the acoustic response in a liquid-filled complex piping network with multiple branches. For illustration, the interactions between two reciprocating pumps operating in a two-branched network are analysed using a one-dimensional linear model. The interactions between sources and acoustic eigenmodes lead to enhanced or suppressed acoustic responses depending on the spatial separation between the sources and their phase differences. The acoustic field measurements from the sweep of driving frequency of a mono-ethylene-glycol (MEG) pump module with two reciprocating pumps in a three-branched network are analysed. The linear model captures the approximate resonance profile of the field measurement data. The presence of plane acoustic wave attenuation in the practical case is influenced by the losses associated with pipe fittings

Analysis and design optimization of an integrated micropump-micromixer operated for bio-MEMS applications

Abstract A generic microfluidic system composed by two single chamber valveless micropumps connected to a simple T-type channel intersection is examined numerically. The characteristics of a feasible valveless micropump have been used in the design, where efficient mixing is produced due to the pulsating flow generated by the micropumps. The advantages of using time pulsing inlet flows for enhancing mixing in channels have been harnessed through the activation of intrinsic characteristics of the pumps required to achieve the periodic flows. A parametric study is carried out on this microfluidic system using Computational Fluids Dynamics (CFD) on a design space defined by a Design-of-Experiments (DOE) technique. The frequency f and the phase difference φ of the periodic fluid velocities (operation parameters) and the angle θ formed by the inlet channels at the intersection (geometric parameter) are used as design parameters, whereas mixing quality, pressure drop and maximum shear strain rate in the channel are the performance parameters. The study identifies design features for which the pressure drop and shear strain are reduced whereas the mixing quality is increased. The proposed microfluidic system achieves high mixing quality with performance parameters that enable manipulation of biological fluids in microchannels