Pressure Losses and Limiting Reynolds Numbers for Non-Newtonian Fluids in Short Square-Edged Orifice Plates

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Butteur Ntamba Ntamba ◽  
Veruscha Fester
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Pressure Losses ◽  
Pressure Loss Coefficient ◽  
Stable Operating ◽  
Piping Systems ◽  
Laminar And Turbulent Flow ◽  
Loss Coefficients ◽  
Industrial Problem

Correlations predicting the pressure loss coefficient along with the laminar, transitional, and turbulent limiting Reynolds numbers with the β ratio are presented for short square-edged orifice plates. The knowledge of pressure losses across orifices is a very important industrial problem while predicting pressure losses in piping systems. Similarly, it is important to define stable operating regions for the application of a short orifice at lower Reynolds numbers. This work experimentally determined pressure loss coefficients for square-edged orifices for orifice-to-diameter ratios of β = 0.2, 0.3, 0.57, and 0.7 for Newtonian and non-Newtonian fluids in both laminar and turbulent flow regimes.

scholarly journals Turbulence model performance for ventilation components pressure losses

2021 ◽  
Author(s):  
Karsten Tawackolian ◽  
Martin Kriegel
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Test Case ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Near Wall

AbstractThis study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

Pressure-Loss Coefficient of 90 deg Sharp-Angled Miter Elbows

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Wameedh T. M. Al-Tameemi ◽  
Pierre Ricco
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Dynamic Pressure ◽  
Reynolds Numbers ◽  
Loss Coefficient ◽  
Straight Pipe ◽  
Pressure Loss Coefficient ◽  
Circular Pipes ◽  
Piping Systems

The pressure drop across 90deg sharp-angled miter elbows connecting straight circular pipes is studied in a bespoke experimental facility by using water and air as working fluids flowing in the range of bulk Reynolds number 500<Re<60,000. To the best of our knowledge, the dependence on the Reynolds number of the pressure drop across the miter elbow scaled by the dynamic pressure, i.e., the pressure-loss coefficient K, is reported herein for the first time. The coefficient is shown to decrease sharply with the Reynolds number up to about Re=20,000 and, at higher Reynolds numbers, to approach mildly a constant K=0.9, which is about 20% lower than the currently reported value in the literature. We quantify this relation and the dependence between K and the straight-pipe friction factor at the same Reynolds number through two new empirical correlations, which will be useful for the design of piping systems fitted with these sharp elbows. The pressure drop is also expressed in terms of the scaled equivalent length, i.e., the length of a straight pipe that would produce the same pressure drop as the elbow at the same Reynolds number.

Loss Coefficients in Microelbows

2009 ◽  
Author(s):  
Tim A. Handy ◽  
Evan C. Lemley ◽  
Dimitrios V. Papavassiliou ◽  
Henry J. Neeman
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Cross Sections ◽  
Pressure Loss ◽  
Reynolds Numbers ◽  
Quantitative Agreement ◽  
Loss Coefficient ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Tube Exit

The goal of this study was to determine laminar pressure loss coefficients for flow in microelbows with circular and trapezoidal cross-sections. Flow conditions and pressure losses in these elbows are of interest in microfluidic devices, in porous media, and in other types of microfluidic networks. The literature focuses almost exclusively on loss coefficients due to turbulent flow in macroelbows with very little data on laminar flow in macroelbows. The pressure loss coefficients determined in this study are intended to aid in realistic simulation of existing laminar flow networks or the design of these networks. This study focused on an elbow of constant cross-section with inlet and outlet tubes of sufficient length so as to allow fully developed laminar flow at the entrance to the elbow and at the outlet tube exit. For the circular elbow, both the ratio of elbow radius to inner diameter and inlet Reynolds number were allowed to vary over the ranges of 0.5—10.5 and 1—2500, respectively. The laminar pressure loss coefficients were determined by simulating incompressible flow over the range of geometries and Reynolds numbers in the commercial CFD software FLUENT. The pressure and velocity distributions in the inlet and outlet tubes were averaged at multiple upstream and downstream positions, and were then used to extrapolate the loss coefficient due to the elbow. The results showed that the loss coefficient for larger ratios tended to be higher, in some cases in excess of 100, at low Reynolds number flows, but as the flow approached the transitional regime, the loss coefficients leveled out to roughly their accepted turbulent values of between 0.4 and 1.0. These results show good qualitative and quantitative agreement with limited laminar elbow experimental data available for macroelbows. For the trapezoidal elbows the loss coefficient levels off to about two for Reynolds numbers greater than 100.

Simulations to Determine Laminar Loss Coefficients for Flow in Circular Ducts With Arbitrary Planar Bifurcation Geometries

2008 ◽  
Author(s):  
Tim A. Handy ◽  
Evan C. Lemley ◽  
Dimitrios V. Papavassiliou ◽  
Henry J. Neeman
Keyword(s):  
Pressure Loss ◽  
Three Dimensional ◽  
Computer Code ◽  
Two Dimensions ◽  
Stagnation Pressure ◽  
Loss Coefficient ◽  
Pressure Losses ◽  
Common Plane ◽  
Loss Coefficients ◽  
Inlet Duct

The goal of this study was to determine laminar stagnation pressure loss coefficients for circular ducts in which flow encounters a planar bifurcation. Flow conditions and pressure losses in these laminar bifurcations are of interest in microfluidic devices, in porous media, and in other networks of small ducts or pores. Until recently, bifurcation geometries had been studied almost exclusively for turbulent flow, which is often found in fluid supply and drain systems. Recently, pressure loss coefficients from simulations of a few arbitrary bifurcation geometries in two-dimensions have been published — the present study describes the extension of these two-dimensional simulations to three-dimensional circular ducts. The pressure loss coefficients determined in this study are intended to allow realistic simulation of existing laminar flow networks or the design of these networks. This study focused on a single inlet duct with two outlet ducts, which were allowed to vary in diameter, flow fraction, and angle — all relative to the inlet duct. All ducts considered in this study were circular with their axes in a common plane. Laminar stagnation pressure loss coefficients were determined by simulating incompressible flow through 475 different geometries and flow condition combinations. In all cases, the flow was laminar in the inlet and outlet ducts with a Reynolds number of 15 in the inlet duct. Simulations of the dividing flow geometries were done using FLUENT and a custom written computer code, which automated the process of creating the three-dimensional flow geometries. The outputs, pressure and velocity distributions at the inlet and outlets, were averaged over the circular ducts and then used to calculate pressure loss coefficients for each of the geometries and flow fraction scenarios simulated. The results for loss coefficient for the geometries considered ranged from 2.0 to 70. The loss coefficient for any geometry increased significantly as the outlet flow fraction increased. A consistent increase in loss coefficient was also observed as a function of decreasing outlet duct diameter. Less significant variation of the loss coefficient was observed as a function of the angles of the outlet ducts.

Effects of Bio-Inspired Micro-Scale Surface Patterns on the Profile Losses in a Linear Cascade

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Qiang Liu ◽  
Shan Zhong ◽  
Lin Li
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Loss Reduction ◽  
Turning Angle ◽  
Low Reynolds Numbers ◽  
Linear Cascade ◽  
Micro Scale ◽  
Pressure Loss Coefficient ◽  
Surface Patterns ◽  
Scale Surface

Abstract In this paper, we investigated the effects of herringbone riblets, a type of bio-inspired micro-scale surface patterns, on pressure losses and flow turning angles in a linear cascade over a range of low Reynolds numbers from 0.50 × 105 to 1.50 × 105 and at three different incidence angles. Our experiments showed that despite their micro-scale size, herringbone riblets produced a significant reduction in pressure loss and a substantial increase in flow turning angle except at the low end of the Reynolds numbers tested. In comparison to the baseline case without riblets, the highest reduction in the zone-averaged pressure loss coefficient behind one flow passage was 36.4% which was accompanied by a 4.1 deg increase in the averaged turning angle. The loss reduction was caused by a decrease in γmax at α = −1 deg, a narrower wake zone at α = 9 deg and a mixture of both at α = 4 deg due to the suppression of flow separation on the blade suction surface. It was also noted that such a significant improvement was always accompanied by the appearance of a serrated wake structure in the contours of pressure loss coefficient in which the region with a higher loss reduction occurring directly behind the divergent region of herringbone riblets. The observed improvement in cascade performance was attributed to the secondary flow motion produced by herringbone riblets which energizes the boundary layer. Overall, this work has produced convincing experimental evidence that herringbone riblets could be potentially used as passive flow control devices for reducing flow separation in compressors at low Reynolds numbers.

Transient Pressure Loss in Compressor Station Piping Systems

2010 ◽  
Author(s):  
Klaus Brun ◽  
Marybeth Nored ◽  
Dennis Tweten ◽  
Rainer Kurz
Keyword(s):  
Pressure Loss ◽  
Dynamic Pressure ◽  
Piping System ◽  
Flow Profile ◽  
Fluid Models ◽  
Reciprocating Compressor ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Pressure Losses ◽  
Piping Systems

“Dynamic pressure loss” is often used to describe the added loss associated with the time varying components of an unsteady flow through a piping system in centrifugal and reciprocating compressor stations. Conventionally, dynamic pressure losses are determined by assuming a periodically pulsating 1-D flow profile and calculating the transient pipe friction losses by multiplying a friction factor by the average flow dynamic pressure component. In reality, the dynamic pressure loss is more complex and is not a single component but consists of several different physical effects, which are affected by the piping arrangement, structural supports, piping diameter, and the level of unsteadiness in the flow stream. The pressure losses due to fluid-structure interactions represent one of these physical loss mechanisms and are presently the most misrepresented loss term. The dynamic pressure losses, dominated at times by the fluid-structure interactions, have not been previously quantified for transient flows in compressor piping systems. A number of experiments were performed by SwRI utilizing an instrumented piping system in a compressor closed loop facility to determine this loss component. Steady and dynamic pressure transducers and on-pipe accelerometers were utilized to study the dynamic pressure loss. This paper describes findings from reciprocating compressor experiments and the various fluid modeling studies undertaken for the same piping system. The objective of the research was to quantitatively assess the individual pressure loss components which contribute to dynamic pressure (non-steady) loss based on their physical basis as described by the momentum equation. Results from these experiments were compared to steady state and dynamic pressure loss predictions from 1-D and 3-D fluid models (utilizing both steady and transient flow conditions to quantify the associated loss terms). Comparisons between the fluid model predictions and experiments revealed that pressure losses associated with the piping fluid-structure interactions can be significant and may be unaccounted for by advanced 3-D fluid models. These fluid-to-structure losses should not be ignored when predicting dynamic pressure loss. The results also indicated the ability of an advanced 1-D Navier Stokes solution at predicting inertial momentum losses. Correspondingly, the three-dimensional fluid models were able to capture boundary layer losses affected by 3-D geometries.

Flow Around Baffles

1984 ◽  
Vol 106 (4) ◽  
pp. 743-749 ◽  
Author(s):  
C. Berner ◽  
F. Durst ◽  
D. M. McEligot
Keyword(s):  
Flow Visualization ◽  
Water Flow ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Laser Doppler Anemometry ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
Streamwise Direction ◽  
Loss Coefficients ◽  
Shell And Tube

Flow visualization, manometry, and laser-Doppler anemometry have been applied to approximately two-dimensional water flow around segmental baffles with baffle spacing/depth equal to 0.4, window cuts from 10 to 50 percent, and Reynolds numbers ranging from 600–10,500 in order to simulate important aspects relating to shellside flow in shell-and-tube heat exchangers. The main features of the flow (which is eventually periodic in the streamwise direction), development lengths, pressure loss coefficients, and mean and rms velocity distributions are presented.

scholarly journals Preliminary Experimental Study on Pressure Loss Coefficients of Exhaust Manifold Junction

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Xiao-lu Lu ◽  
Kun Zhang ◽  
Wen-hui Wang ◽  
Shao-ming Wang ◽  
Kang-yao Deng
Keyword(s):  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Flow Ratio ◽  
Pressure Loss Coefficient ◽  
Loss Coefficients ◽  
Total Pressure Loss Coefficient ◽  
Mass Flow Ratio

The flow characteristic of exhaust system has an important impact on inlet boundary of the turbine. In this paper, high speed flow in a diesel exhaust manifold junction was tested and simulated. The pressure loss coefficient of the junction flow was analyzed. The steady experimental results indicated that both of static pressure loss coefficientsL13andL23first increased and then decreased with the increase of mass flow ratio of lateral branch and public manifold. The total pressure loss coefficientK13always increased with the increase of mass flow ratio of junctions 1 and 3. The total pressure loss coefficientK23first increased and then decreased with the increase of mass flow ratio of junctions 2 and 3. These pressure loss coefficients of the exhaust pipe junctions can be used in exhaust flow and turbine inlet boundary conditions analysis. In addition, simulating calculation was conducted to analyze the effect of branch angle on total pressure loss coefficient. According to the calculation results, total pressure loss coefficient was almost the same at low mass flow rate of branch manifold 1 but increased with lateral branch angle at high mass flow rate of branch manifold 1.

The Effect of Reynolds and Mach Number on End-Wall Profiling Performance

2010 ◽  
Author(s):  
Rau´l Va´zquez ◽  
Vicente Jerez Fidalgo
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Stagnation Pressure ◽  
Airfoil Surface ◽  
Pressure Losses ◽  
Physical Mechanisms ◽  
Wide Range ◽  
Mach Numbers ◽  
Turbine Airfoils ◽  
End Wall

This paper shows an experimental back-to-back comparison carried out between two annular cascades of identical turbine airfoils operating at the same flow conditions; one of them had axysimmetric endwalls and, the other, non-axysimmetric. The annular cascades consisted of 100 high lift, high aspect ratio and high turning blades that are characteristic of modern low pressure (LP) turbines. Upstream and downstream data were obtained with miniature pneumatic probes. The static pressure fields on the airfoil surface and the end-walls were measured with more than 200 sensors. The motivation of this work is to improve the understanding of profiled end-wall performance in the following three aspects: A. Explore the performance of profiled non-axysimmetric end-walls at off design conditions, namely its sensitivity to Reynolds and Mach numbers, analyzing how the turbine characteristics are modified. For that purpose, the experiment was carried out for a wide range of Reynolds numbers, extending from 120k to 315k, and exit Mach numbers, extending from 0.5 to 0.9. B. Determine experimentally the stagnation pressure loss improvement due to profiled non-axysimmetric end-walls in a relevant environment. C. Investigate further the physical mechanisms that govern the variation of stagnation pressure losses of profiled end-walls. CFD results are presented and are compared with experimental results in terms of total pressure loss, helicity and SKEH.

Modeling of Newtonian Fluids in Annular Geometries With Inner Pipe Rotation

2010 ◽  
Author(s):  
Mehmet Sorgun ◽  
Jerome J. Schubert ◽  
Ismail Aydin ◽  
M. Evren Ozbayoglu
Keyword(s):  
Axial Velocity ◽  
Pressure Loss ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Newtonian Fluids ◽  
Flow Loop ◽  
Eccentric Annulus ◽  
Pressure Losses ◽  
Proposed Model ◽  
Pipe Rotation

Flow in annular geometries, i.e., flow through the gap between two cylindrical pipes, occurs in many different engineering professions, such as petroleum engineering, chemical engineering, mechanical engineering, food engineering, etc. Analysis of the flow characteristics through annular geometries is more challenging when compared with circular pipes, not only due to the uneven stress distribution on the walls but also due to secondary flows and tangential velocity components, especially when the inner pipe is rotated. In this paper, a mathematical model for predicting flow characteristics of Newtonian fluids in concentric horizontal annulus with drill pipe rotation is proposed. A numerical solution including pipe rotation is developed for calculating frictional pressure loss in concentric annuli for laminar and turbulent regimes. Navier-Stokes equations for turbulent conditions are numerically solved using the finite differences technique to obtain velocity profiles and frictional pressure losses. To verify the proposed model, estimated frictional pressure losses are compared with experimental data which were available in the literature and gathered at Middle East Technical University, Petroleum & Natural Gas Engineering Flow Loop (METU-PETE Flow Loop) as well as Computational Fluid Dynamics (CFD) software. The proposed model predicts frictional pressure losses with an error less than ± 10% in most cases, more accurately than the CFD software models depending on the flow conditions. Also, pipe rotation effects on frictional pressure loss and tangential velocity is investigated using CFD simulations for concentric and fully eccentric annulus. It has been observed that pipe rotation has no noticeable effects on frictional pressure loss for concentric annuli, but it significantly increases frictional pressure losses in an eccentric annulus, especially at low flow rates. For concentric annulus, pipe rotation improves the tangential velocity component, which does not depend on axial velocity. It is also noticed that, as the pipe rotation and axial velocity are increased, tangential velocity drastically increases for an eccentric annulus. The proposed model and the critical analysis conducted on velocity components and stress distributions make it possible to understand the concept of hydro transport and hole cleaning in field applications.

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