Effect of Polymeric Additives on Turbulent Flow in Opposed Jets

1995 ◽  
Vol 48 (11S) ◽  
pp. S216-S221 ◽  
Author(s):  
A. J. Mu¨ller ◽  
A. E. Saez ◽  
J. P. Tatham ◽  
J. A. Odell
Keyword(s):  
Pressure Drop ◽  
Turbulent Flow ◽  
Flow Rate ◽  
Molecular Conformation ◽  
Rate Of Change ◽  
Newtonian Fluids ◽  
Transition To Turbulence ◽  
Random Coil ◽  
Polymer Addition ◽  
Polymeric Additives

In this work we study the effect of polymeric additives on the transition to turbulence in opposed-jets flow. In this type of flow, the transition to turbulence for Newtonian fluids is characterized by a decrease in the rate of change of pressure drop with flow rate. We have used various polymers whose equilibrium molecular conformation in aqueous solution is different: poly (ethylene oxide), which exists in a conformation close to a random coil, hydroxypropyl guar, which adopts an expanded coil conformation, and hydrolyzed polyacrylamide, whose conformation is close to a random coil in the presence of an electrolyte (sodium chloride) but it changes to an expanded coil in distilled water. The results show that small amounts of either flexible or semi-rigid polymers induce a delay in the critical Reynolds number at which turbulence sets in. This delay seems to be a result of the suppression of flow instabilities in a region close to the stagnation point, which is linked to macromolecular orientation. Since, for Newtonian fluids, this flow has an increase of drag with flow rate that is slower in the turbulent flow regime than in the laminar regime, the addition of polymer causes a substantially higher pressure drop in turbulent flow with respect to that of the pure solvent. Therefore, polymer addition causes, in this particular case, a drag increase in turbulent flow, as opposed to the commonly observed drag reduction in turbulent flow through pipes.

scholarly journals Pressure Drop Method as a Useful Tool for Detecting Rheological Properties of Non-Newtonian Fluids during Flow

2021 ◽  
Vol 11 (14) ◽  
pp. 6583
Author(s):  
Kacper Kaczmarczyk ◽  
Joanna Kruk ◽  
Paweł Ptaszek ◽  
Anna Ptaszek
Keyword(s):  
Pressure Drop ◽  
Rheological Properties ◽  
Flow Rate ◽  
Pressure Sensors ◽  
Newtonian Fluids ◽  
Measuring System ◽  
Flow Meter ◽  
Rotational Rheometer ◽  
Drop Method ◽  
Measuring Section

The aim of the research was to develop a pressure drop measuring method dedicated to fluids under real flow through a pipeline. The measurement system is a set of appropriately configured flow meter and pressure sensors installed on the pipeline. The pressure drop values detected on the measuring section are sufficient to clearly determine the rheological properties of the fluid. The measuring system used for the tests consisted of a screw pump, two pressure sensors and an electromagnetic flow meter. The length of the measuring section was 4.12 m, and the internal diameter of the pipeline was 0.026 m. To calibrate of the measuring system a glycerol was used. As a model fluid, a 1% water solution of xanthan gum was used and was subjected to the flow at following shear rate conditions: 5, 11, 17, 23, 29, 35, 41, 47, 53, 59, 65 s−1. The obtained raw experimental data included the pressure drop values and flow rate and they created full information about the fluid behavior during flow. According to the momentum balance equation, the rheological parameters of Ostwald de Waele model were estimated. The estimation procedure was carried out with the help of the Marquardt-Levenberg minimisation method. The same solutions simultaneously were tested with the help of a rotational rheometer. The data obtained from the pressure drop method were consistent with the results obtained from the rotational rheometer. The use of the pressure drop allows to determine the rheological properties of the non-newtonian fluids under the process conditions directly in the pipeline. In addition, it is possible to perform full rheological characteristics based on one flow rate under laminar conditions.

Preparation of Silk Fibroin Microspheres

2011 ◽  
Vol 236-238 ◽  
pp. 1902-1905 ◽  
Author(s):  
Lu Wang ◽  
Zhen Ran Xia ◽  
Lin Lin Lv ◽  
Qiang Tang ◽  
Ming Zhong Li
Keyword(s):  
Silk Fibroin ◽  
Flow Rate ◽  
Molecular Conformation ◽  
Solution Concentration ◽  
Random Coil ◽  
Ethanol Treatment ◽  
Drying Method ◽  
Sphere Size ◽  
Ft Ir ◽  
Fibroin Solution

TheBombyx morisilk fibroin microspheres with controllable size were prepared by electrostatic spraying and freeze-drying method. The effects of solution concentration, voltage and flow rate on the sphere size were discussed. The morphology of microspheres was observed by scanning electron microscopy (SEM). The influence of ethanol treatment on the molecular conformation of silk fibroin microspheres was investigated by XRD and FT-IR spectra. The results indicated that the silk fibroin microspheres with diameter in range of 117-363 μm were spherical in shape, and there were plenty of pores both on the surface and in the interior of the microspheres. The sphere size increased with the rising of silk fibroin solution concentration and flow rate, while decreased as the voltage enhanced. The conformation of silk fibroin microspheres changed from random coil to silk II structure after ethanol treatment.

On the Stability of Slip Flows in Parallel Heated Passages

1969 ◽  
Vol 91 (4) ◽  
pp. 549-553 ◽  
Author(s):  
C. A. Rhodes
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Heat Input ◽  
Rate Of Change ◽  
Inlet Temperature ◽  
Constant Heat ◽  
The Stability ◽  
Slip Flows

Rarified flows in heated passages are shown to have instabilities under certain conditions similar to those occurring with laminar continuum flows. As in the case of continuum flows these instabilities occur where the rate of change of pressure drop with mass flow rate at constant heat input is negative. As gases become more highly rarified, the slope of the pressure drop with flow rate no longer becomes negative and flows are stable. Stability regions are defined by the ratio of outlet to inlet temperature, Knudsen number at the inlet to the passage, and the product of Reynolds number at the inlet and diameter-to-length ratio.

HEAT TRANSFER AND PRESSURE DROP IN TURBULENT FLOW THROUGH A TUBE WITH LONGITUDINAL PERFORATED STAR-SHAPED INSERTS

2011 ◽  
Vol 18 (6) ◽  
pp. 491-502 ◽  
Author(s):  
Andrew Mintu Sarkar ◽  
M. A. Rashid Sarkar ◽  
Mohammad Abdul Majid
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Flow Through

Study of fluid flow through a channel deformed by piezoelement

2018 ◽  
Vol 13 (3) ◽  
pp. 1-10 ◽  
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh Nasibullaeva ◽  
O.V. Darintsev
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Boundary Conditions ◽  
Flow Rate ◽  
Contact Surface ◽  
Piezoelectric Element ◽  
Neumann Boundary ◽  
Differential Pressure ◽  
Physical Parameters ◽  
Flow Through

The flow of a liquid through a tube deformed by a piezoelectric cell under a harmonic law is studied in this paper. Linear deformations are compared for the Dirichlet and Neumann boundary conditions on the contact surface of the tube and piezoelectric element. The flow of fluid through a deformed channel for two flow regimes is investigated: in a tube with one closed end due to deformation of the tube; for a tube with two open ends due to deformation of the tube and the differential pressure applied to the channel. The flow rate of the liquid is calculated as a function of the frequency of the deformations, the pressure drop and the physical parameters of the liquid.

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