Search results for "flow [Keywords]"
showing 10 items of 469 documents
The Effects of Flow Waveform on Oxygenation in Pediatric Patients
2015
RAPID CONDENSATIONAL GROWTH OF PARTICLES IN THE INLET OF PARTICLE SIZING INSTRUMENTS
2000
Abstract Rapid particle growth by the condensation of water vapour resulting from expansion in the inlet of particle sizing instruments such as optical particle counters and impactors was modelled. The corrected Mason diffusion growth equation extended to the application for particles beyond the continuum region has been found suitable. The influence of particle acceleration in the nozzle air flow, modelled with the CFX-FLOW3D program, on the condensation process was considered. The study was focused on a typical inlet nozzle of an optical particle counter with an inner diameter of 0.5 mm and a length of 20 mm, connected by an additional 20 mm long conical nozzle at a flow rate of 28.5 ml s…
Heat transfer and flow resistance for stacked wire gauzes: Experiments and modelling
2012
Abstract The study deals with the flow resistance and heat transport properties of woven and knitted wire gauzes stacked in a tubular apparatus. The experimental programme included flow resistance and heat transfer experiments performed for air flow ( Re = 2–300) using three woven gauzes and one knitted gauze. During the heat transfer experiments, the gauzes were heated by electric current flowing directly through them. The models describing the flow resistance and the heat transfer were put forward. Both the models base on the concept of the laminar flow developing in a short capillary channel (i.e. the gauze mesh). The model describing the flow resistance does not contain the experimenta…
The Nukiyama Curve in Water Spray Cooling: its Derivation from Temperature-Time Histories and its Dependence on the Quantities that Characterize Drop…
2007
Abstract Heat transfer from hot aluminium walls to cold water sprays was investigated. The method used was the transient two-side symmetric cooling of a planar aluminium target, previously heated to temperatures of up to 750 K, by twin sprays issuing from full-cone swirl spray nozzles of various gauge. The target’s mid-plane temperature was recorded during the cooling transient by thin-foil K thermocouples and a high-frequency data acquisition system. In order to determine the wall temperature Tw, the wall heat flux q w ″ and the q w ″ - T w heat transfer (Nukiyama) curve, two different approaches were used: the first was based on the solution of an inverse heat conduction problem, the seco…
Numerical simulation of reciprocating turbulent flow in a plane channel
2009
Direct numerical simulation results were obtained for oscillatory flow with zero time mean (reciprocating flow) in a plane channel using a finite volume method, Crank-Nicolson time stepping and central approximation of the advection terms. A pressure gradient varying co-sinusoidally in time was imposed as the forcing term, and its frequency and amplitude were made to vary so as to span a range of regimes from purely laminar to fully turbulent. For the limiting cases of reciprocating laminar flow and steady-state turbulent flow, numerical results were validated against analytical solutions and classic experimental literature data, respectively. For general reciprocating flows, predictions we…
Dynamic mode decomposition of magnetohydrodynamic bubble chain flow in a rectangular vessel
2021
We demonstrate the first application of dynamic mode decomposition (DMD) to bubble flow with resolved dynamic liquid/gas boundaries. Specifically, we have applied DMD to the output of numerical simulations for a system where chains of bubbles ascend through a rectangular liquid metal vessel. Flow patterns have been investigated in the vessel and bubble reference frames. We show how gas flow rate and applied magnetic affect bubble wake flow and larger-scale flow structures within the liquid metal vessel by examining the velocity field mode statistics over trajectory time and total flow time as well as the computed mode velocity fields. The results of this proof-of-concept study indicate that…
Engineering Polymer Microparticles by Droplet Microfluidics
2013
Capillary-based flow-focusing and co-flow microsystems were developed to produce sphere-like polymer microparticles of adjustable sizes in the range of 50 to 600 μm with a narrow size distribution (CV < 5%) and different morphologies (core-shell, janus, and capsules). Rod-like particles whose length was conveniently adjusted between 400 μm and few millimeters were also produced using the same microsystems. Influence of operating conditions (flow rate of the different fluid, microsystem characteristic dimensions, and design) as well as material parameters (viscosity of the different fluids and surface tension) was investigated. Empirical relationships were thus derived from experimental data…
Flexible vegetation behaviour and effects on flow conveyance: experimental observations
2015
As it is known, vegetation is an important component of aquatic ecosystems. Because of the variety of species and, thus, of the characteristics of the vegetation elements (form, size, stiffness, etc.), it is difficult to develop a widely applicable method to predict mean flow and flow resistance. Despite the intense activity research, much work has to be done in understanding hydrodynamics in vegetated channels. This is important to analyse many physical processes involved in the ecosystem at different spatial and time scales. In this paper, attention is restricted to flexible vegetation. After a brief description of results obtained in previous experimental works conducted in a rectangular…
Adaptive PI Control of Bottom Hole Pressure during Oil Well Drilling
2018
Abstract In this paper, we studied the bottom hole pressure (BHP) control in an oil well during drilling. Today marginal wells with narrow pressure windows are frequently being drilled. This requires accurate and precise control to balance the bottom hole pressure between the pore and fracture pressure of the reservoir. This paper presents three control schemes to stabilize the BHP prole, including proportional-integral(PI) control, PI with feed-forward control and adaptive PI with feed-forward control. The proposed schemes are carried out through simulations on a high-fidelity hydraulic drilling simulator for flow rate changes and BHP set-point changes. In fast set-point changes and flow r…
Improved resolution power of electrophoretic fractionation of DNA using a voltage gradient up and down application
2004
The improved resolution power of electrophoretic fractionation of DNA in a wide range of molecular masses is demonstrated using an "up and down" application of voltage gradient gel electrophoresis (VGGE). This application also allows separation of different DNA fragments which are poorly fractionated in conventional electrophoresis.