The Flow and Decay Behavior of a Submerged Shear-Thinning Jet With Yield Stress

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Yield Stress ◽  
Numerical Solutions ◽  
Shear Thinning ◽  
Momentum Conservation ◽  
Recirculation Region ◽  
Centerline Velocity ◽  
Flow Recirculation ◽  
Shear Thinning Fluids ◽  
Submerged Jets ◽  
The Impact

The flow and decay characteristics of submerged jets of shear-thinning fluids with yield stress are studied. Numerical solutions to the governing mass and momentum conservation equations, along with the Herschel–Bulkley rheological model, are obtained using a finite-difference scheme. A parametric study is implemented to investigate the influence of flow inertia and rheology over the following range of parameters: Reynolds number, 50 ≤ Re ≤ 200; yield number, 0 ≤ Y ≤ 1; and shear-thinning index, 0.6 ≤ n ≤ 1. A large recirculation region exists for Newtonian and shear-thinning non-Newtonian jets. However, the extent and strength of the recirculation region substantially diminish with the yield number and, to a lesser extent, when the shear-thinning index is reduced from 1 to 0.6. Increasing the yield number beyond a critical value eliminates flow recirculation. The centerline velocity and momentum decay of shear-thinning jets with yield stress, in general, increase with the yield number. Velocity- and momentum-based depths of penetration, DPU, and DPM, respectively, are introduced and presented. DPU and DPM are the downstream locations corresponding to 90% decay in the initial centerline velocity and jet momentum, respectively. A substantial decrease in DPU and DPM is observed when the shear-thinning index is reduced from 1 to 0.6 for Y = 0. The presence of yield stress significantly reduces both DPU and DPM of submerged jets. The impact of shear-thinning on the decay characteristics of the jet is more pronounced at low yield numbers.

Velocity and Momentum Decay Characteristics of Submerged Yield-Pseudoplastic Jets

2015 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Numerical Solutions ◽  
Shear Thinning ◽  
Critical Value ◽  
Momentum Conservation ◽  
Recirculation Region ◽  
Centerline Velocity ◽  
Flow Recirculation ◽  
Submerged Jets ◽  
Flow Inertia ◽  
The Impact

The velocity and momentum decay characteristics of submerged yield-pseudoplastic jets are studied. Numerical solutions to the governing mass and momentum conservation equations, along with the Herschel-Bulkley rheological model, are obtained using a finite-difference scheme. A parametric study is implemented to investigate the influence of flow inertia and rheology over the following range of parameters: Reynolds number, 50 ≤ Re ≤ 200, Yield number, 0 ≤ Y ≤ 1, and shear-thinning index, 0.6 ≤ n ≤ 1. A large recirculation region exists for Newtonian and pseudoplastic non-Newtonian jets. However, the extent and strength of the recirculation region substantially diminish with the yield number and, to a lesser extent, when the shear-thinning index is reduced from 1 to 0.6. Increasing the yield number beyond a critical value eliminates flow recirculation. The centerline velocity and momentum decay of yield-pseudoplastic jets, in general, increases with the yield number. Velocity and momentum based depths of penetration, DPU and DPM, respectively, are extracted and presented. A substantial decrease in DPU and DPM is observed when the shear-thinning index is reduced from 1 to 0.6 for Y = 0. The presence of yield stress significantly reduces both DPU and DPM of submerged jets. The impact of shear-thinning on the decay characteristics of the jet is more pronounced at low yield numbers.

Flow and Decay Characteristics of Submerged Yield-Pseudoplastic Jets

2014 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Flow Structure ◽  
Numerical Solutions ◽  
Shear Thinning ◽  
Critical Value ◽  
Momentum Conservation ◽  
Recirculation Region ◽  
Centerline Velocity ◽  
General Increase ◽  
Flow Recirculation ◽  
The Impact

The flow structure and decay characteristics of submerged yield-pseudoplastic jets are investigated. Numerical solutions to the governing mass and momentum conservation equations, along with the Herschel-Bulkley rheological model, are obtained using a finite-difference scheme. A large recirculation region exists for Newtonian and pseudoplastic non-Newtonian jets. However, the extent and strength of the recirculation region substantially diminish with the yield number and, to a much lesser extent, when the shear-thinning index is decreased from 1 to 0.6. Increasing the yield number beyond a critical value eliminates flow recirculation. The centerline velocity and momentum decay of yield-pseudoplastic jets, in general, increase with the yield number. The impact of shear-thinning on the flow structure and decay characteristics of the jet is more pronounced at low yield numbers.

Inflow Conditions and Suddenly Expanding Annular Shear-Thinning Flows

2017 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Power Law ◽  
Numerical Solutions ◽  
Shear Thinning ◽  
Diameter Ratio ◽  
Inflow Velocity ◽  
Flow Recirculation ◽  
Shear Thinning Fluids ◽  
Power Law Index ◽  
The Impact ◽  
Inflow Conditions

The impact of inflow conditions on the flow structure and evolution characteristics of annular flows of Newtonian and shear-thinning fluids through a sudden pipe expansion are studied. Numerical solutions to the elliptic form of the governing equations along with the power-law constitutive equation were obtained using a finite-difference scheme. A parametric study is performed to reveal the influence of inflow velocity profiles, annular diameter ratio, k, and power-law index, n, over the following range of parameters: inflow velocity profile = {fully-developed, uniform}, k = {0, 0.5, 0.7} and n = {1, 0.8, 0.6}. Flow separation and entrainment, downstream of the expansion plane, creates central and a much larger outer recirculation regions. The results demonstrate the influence of inflow conditions, annular diameter ratio, and rheology on the extent and intensity of both flow recirculation regions, the wall shear stress distribution, and the evolution and redevelopment characteristics of the flow downstream the expansion plane. Fully-developed inflows result in larger reattachment and redevelopment lengths as well as more intense recirculation, within the central and corner regions, in comparison with uniform inflow conditions.

Influence of Non-Newtonian Rheology on Mass Transfer From a Biofluid in Separated and Reattached Flows

2018 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Mass Transfer ◽  
Yield Stress ◽  
Mass Transfer Rate ◽  
Flow Region ◽  
Shear Thinning ◽  
Recirculation Region ◽  
Transfer Rates ◽  
Separated And Reattached Flow ◽  
The Impact ◽  
Wall Mass

Influence of the rheological model selection on the flow and mass transfer behavior of human blood in a separated and reattached flow region is investigated. Newtonian and non-Newtonian hemorheological models that account for the yield stress and shear-thinning characteristics of blood are used. The conservation of mass, momentum, and species equations as well as the Herschel-Bulkley constitutive equation are solved numerically using a finite-difference scheme. A parametric study is performed to reveal the impact of flow restriction and rheological modelling on blood-borne oxygen exchange with the confining walls. The wall mass transfer rates within the separated and reattached regions display a strong dependency on the used hemorheological model. Newtonian and non-Newtonian models result in a peak wall mass transfer rate within the recirculation region. However, non-Newtonian models that account for the yield stress and shear-thinning effects predict a substantial, highly localized, drop in the wall mass transfer rates of oxygen, at the reattachment point.

scholarly journals Droplet splashing during the impact on liquid pools of shear-thinning fluids with yield stress

2021 ◽  
Vol 33 (11) ◽  
pp. 112106
Author(s):  
Xiaoyun Peng ◽  
Tianyou Wang ◽  
Kai Sun ◽  
Zhizhao Che
Keyword(s):  
Yield Stress ◽  
Shear Thinning ◽  
Shear Thinning Fluids ◽  
Liquid Pools ◽  
The Impact

Influence of a Yield-Shear-Thinning Rheology on the Flow Behavior of Submerged Annular Jets

2020 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Flow Field ◽  
Power Law ◽  
Numerical Solutions ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Momentum Conservation ◽  
Recirculation Region ◽  
Substantial Impact ◽  
Laminar Jet ◽  
Power Law Index

Abstract The flow structure and decay characteristics of submerged annular yield-pseudoplastic jets are investigated. Numerical solutions to the governing mass and momentum conservation equations, along with the Herschel-Bulkley rheological model, are obtained using a finite-difference scheme. A parametric study is implemented to investigate the effects of annular nozzle diameter ratio, κ, the power-law index, n, and yield number, Y, over the following range: κ = {0, 0.5}; n = {1, 0.6}; and Y = {0, 1, 5}. The Reynolds number was fixed at Re = 100, which ensured steady and laminar jet flow conditions throughout the whole flow field. The selected yield number and power-law index values allowed for the investigation of the presence of yield stress and shear-thinning effects on the resulting structure and evolution of the flow field. The results demonstrate the substantial impact of the inflow conditions and rheology on the annular jet evolution, and on the extent of the outer recirculation region and recirculation strength of both the outer and central regions.

The Impact of Hemorheology on Wall Shear Stress in a Separated and Reattached Flow Region

2013 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Yield Stress ◽  
Flow Region ◽  
Shear Thinning ◽  
Progression Rate ◽  
Vortex Center ◽  
Wall Shear ◽  
Separated And Reattached Flow ◽  
The Impact

Wall-bounded separating and reattaching flows are encountered in biological applications dealing with blood flows through arteries and prosthetic devices. Separated and reattached flow regions have been associated in the past with the most common arterial disease, atherosclerosis. Previous studies suggest that local wall shear stress (WSS) patterns affect the location and progression rate of atherosclerotic lesions. A parametric study is performed to investigate the influence of hemorheology on the wall shear stress distribution in a separated and reattached flow region. Recent hemorheological studies quantified and emphasized the yield stress and shear-thinning non-Newtonian characteristics of unadulterated human blood. Numerical solutions to the governing equations that account for yield stress and shear-thinning rheological effects are obtained. A low WSS region is observed around the flow reattachment point while a peak WSS always exists close to the vortex center. The yield shear-thinning hemorheological model always results in the highest observed peak WSS. The yield stress impact on WSS distribution is most pronounced in the case of severe restrictions to the flow.

scholarly journals Mixing of shear-thinning fluids with yield stress in stirred tanks

AIChE Journal ◽  
2006 ◽  
Vol 52 (7) ◽  
pp. 2310-2322 ◽  
Author(s):  
P. E. Arratia ◽  
J. Kukura ◽  
J. Lacombe ◽  
F. J. Muzzio
Keyword(s):  
Yield Stress ◽  
Shear Thinning ◽  
Stirred Tanks ◽  
Shear Thinning Fluids

The impact of different arrangement of molecular chains in term of low and high shear rate’s viscosities on heat and mass flow of Non-Newtonian shear thinning fluids

2021 ◽  
Vol 24 ◽  
Author(s):  
Mohsan Hassan ◽  
Abrar Faisal ◽  
Khurram Javid ◽  
Salah Ud-Din Khan ◽  
Ashfaq Ahmad ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shear Rate ◽  
Boundary Layer Flow ◽  
Shear Thinning ◽  
High Shear Rate ◽  
High Shear ◽  
Carreau Model ◽  
Shear Thinning Fluids ◽  
Layer Flow ◽  
The Impact

Background: Non-Newtonian fluids, especially shear thinning fluids, have several applications in the polymer industry, food industry, and even in everyday life. The viscosity of shear thinning fluids is sometimes decreased by two or three orders of magnitude due to the alignment of the molecules in order when the shear rate is increased, and it cannot be ignored in the case of polymer processing and lubrication problems. Objective: So, the effects of viscosities at a low and high shear rate on the heat and mass boundary layer flow of shear thinning fluid over moving belts is investigated in this study. For this proposed, the generalized Carreau model of viscosity relates to shear rate and is used in the momentum equation. The Carreau model contains the five parameters: low shear rate viscosity, high shear rate viscosity, viscosity curvature, consistency index, and flow behavior index. For the heat flow, expression of the thermal conductivity model, similar to the viscosity equation due to the non-Newtonian nature of the fluid, is used in the energy equation. Methods: On the mathematical model of the problem, boundary layer approximations are applied and then simplified by applying the similarity transformations to get the solution. The solution of the simplified equations is obtained by numerical technique RK-Shooting Method. The results are compared with existing results for limited cases and good agreement is found. Results : The results are obtained in the form of velocity and temperature profiles under the impact of all the viscosity’s parameters and are displayed in graphical form. Moreover, the boundary layer parameters such as the thickness of the regions, momentum thickness, and displacement thickness are calculated to understand the structure of the boundary layer flow of fluid. Conclusion: The velocity and temperature of the fluid are decreased and increased respectively by all viscosity’s parameters of the model. So, the results of the boundary layer fluid flow under rheological parameters will not only help engineers to design superior chemical equipment, but will also help improve the economy and efficiency of the overall process.

Sign in / Sign up

Export Citation Format

Share Document