Studies on Unsteady Pressure Fields in the Region of Separating and Reattaching Flows

1990 ◽  
Vol 112 (4) ◽  
pp. 402-408 ◽  
Author(s):  
H. S. Govinda Ram ◽  
V. H. Arakeri
Keyword(s):  
Pressure Fluctuation ◽  
Experimental Studies ◽  
Axisymmetric Body ◽  
Two Dimensional ◽  
Pressure Surface ◽  
Pressure Fields ◽  
Maximum Value ◽  
Mean Pressure ◽  
Surface Fluctuation ◽  
Body Shapes

Experimental studies on the measurement of pressure fields in the region of separating and reattaching flows behind several two-dimensional fore-bodies and one axisymmetric body are reported. In particular, extensive measurements of mean pressure, surface pressure fluctuation, and pressure fluctuation within the flow were made for a series of two-dimensional fore-body shapes consisting of triangular nose with varying included angle. The measurements from different bodies are compared and one of the important findings is that the maximum values of rms pressure fluctuation levels in the shear layer approaching reattachment are almost equal to the maximum value of the surface fluctuation levels.

ANALYSIS OF THE ERROR IN DETERMINING THE EQUIVALENT SIZE OF A DEFECT BY THE STANDARDLESS METHOD DURING ULTRASONIC TESTING

2021 ◽  
pp. 50-57
Author(s):  
A. N. Kireev ◽  
M. A. Kireeva
Keyword(s):  
Relative Error ◽  
High Reliability ◽  
Ultrasonic Method ◽  
Experimental Studies ◽  
Standard Samples ◽  
Defect Identification ◽  
Identification Method ◽  
Maximum Value ◽  
Software Product ◽  
The Relationship

The article provides a review and analysis of the defect identification method for determining the size of discontinuities when diagnosing various machine parts and units by the manual ultrasonic method. This method makes it possible to determine the equivalent size of discontinuities of various types without using standard samples of an enterprise: point planar and volumetric; extended planar and volumetric. The method is based on the use of the relationship between the amplitude and time characteristics of the echo signal from the discontinuity and the backside signal in the object being diagnosed and the equivalent size of the discontinuity. The article presents the mathematical apparatus for the implementation of this method. Also presented is a software product that allows you to automate calculations when using this defect identification method. The article contains experimental studies of the method for determining the equivalent dimensions of discontinuities of various types, which have shown its high reliability. The maximum value of the relative error in determining the equivalent size of a point planar discontinuity was 2.867 %. The maximum value of the relative error in determining the equivalent size of a point volumetric discontinuity was 1.986 %. The maximum value of the relative error in determining the transverse equivalent size of an extended planar discontinuity was 0.667 %. The maximum value of the relative error in determining the transverse equivalent size of an extended volumetric discontinuity was 1.95 %.

Dripping instability of a two-dimensional liquid film under an inclined plate

2021 ◽  
Vol 932 ◽  
Author(s):  
Guangzhao Zhou ◽  
Andrea Prosperetti
Keyword(s):  
Liquid Film ◽  
Initial Conditions ◽  
Strong Dependence ◽  
Bond Number ◽  
Quasi Equilibrium ◽  
Two Dimensional ◽  
Inclined Plate ◽  
Maximum Value ◽  
Critical Curvature ◽  
Rayleigh Taylor Instability

It is known that the dripping of a liquid film on the underside of a plate can be suppressed by tilting the plate so as to cause a sufficiently strong flow. This paper uses two-dimensional numerical simulations in a closed-flow framework to study several aspects of this phenomenon. It is shown that, in quasi-equilibrium conditions, the onset of dripping is closely associated with the curvature of the wave crests approaching a well-defined maximum value. When dynamic effects become significant, this connection between curvature and dripping weakens, although the critical curvature remains a useful reference point as it is intimately related to the short length scales promoted by the Rayleigh–Taylor instability. In the absence of flow, when the film is on the underside of a horizontal plate, the concept of a limit curvature is relevant only for small liquid volumes close to a critical value. Otherwise, the drops that form have a smaller curvature and a large volume. The paper also illustrates the peculiarly strong dependence of the dripping transition on the initial conditions of the simulations. This feature prevents the development of phase maps dependent only on the governing parameters (Reynolds number, Bond number, etc.) similar to those available for film flow on the upper side of an inclined plate.

JUSTIFICATION OF HYDROCYCLONE DESIGN FOR WASTE WATER PURIFICATION

2021 ◽  
Author(s):  
Владимир Александрович Савчук ◽  
Сергей Ильдусович Валеев
Keyword(s):  
Waste Water ◽  
Water Purification ◽  
Experimental Studies ◽  
Optimal Conditions ◽  
Pressure Fields ◽  
Light Impurities

Проведены экспериментальные исследования полей скоростей и давлений в цилиндрическом гидроциклоне для разделения эмульсий с малым содержанием легких примесей (не более 1%). Полученные данные позволяют сделать вывод, что в цилиндрическом гидроциклоне по сравнению с цилиндроконическим гидроциклоном обеспечиваются оптимальные условия для сепарации жидких частиц. Experimental studies of velocity and pressure fields in a cylindrical hydrocyclone for the separation of emulsions with a low content of light impurities (no more than 1%) have been carried out. The data obtained allow us to conclude that in a cylindrical hydrocyclone, in comparison with a cylindrical-conical hydrocyclone, optimal conditions are provided for the separation of liquid particles.

scholarly journals Theoretical and experimental studies of highly selective planar two-dimensional Bragg structures based on dielectric waveguides in the terahertz frequency range

2019 ◽  
Vol 30 ◽  
pp. 07009
Author(s):  
Naum Ginzburg ◽  
Nikolay Peskov ◽  
Vladislav Zaslavsky ◽  
Ekaterina Kocharovskaya ◽  
Andrey Malkin ◽  
...  
Keyword(s):  
Bragg Reflection ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Dielectric Waveguides ◽  
Two Dimensional ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range ◽  
Three Dimensional Modeling ◽  
Bragg Structures

Based on theoretical approach and three-dimensional modeling using the CST Microwave Studio code, planar dielectric two-dimensional Bragg structures in terahertz frequency range were developed and manufactured. Proof-of-principle electrodynamic experiments on the “cold” testing of these structures were carried out. It is shown that the experimental results are in good agreement with the theoretical predicts, including the existence of the highest Q mode inside the Bragg reflection band in the absence of periodicity defects.

A numerical investigation of fluid flows induced by the oscillations of thin plates and evaluation of the associated hydrodynamic forces

2019 ◽  
Vol 874 ◽  
pp. 1057-1095 ◽  
Author(s):  
Artem N. Nuriev ◽  
Airat M. Kamalutdinov ◽  
Andrey G. Egorov
Keyword(s):  
Stokes Equations ◽  
Experimental Studies ◽  
Flow Regimes ◽  
Hydrodynamic Forces ◽  
Thin Plates ◽  
Oscillatory Process ◽  
Dimensionless Frequency ◽  
Two Dimensional ◽  
Wide Range ◽  
Hydrodynamic Influence

The paper is devoted to the problem of harmonic oscillations of thin plates in a viscous incompressible fluid. The two-dimensional flows caused by the plate oscillations and their hydrodynamic influence on the plates are studied. The fluid motion is described by the non-stationary Navier–Stokes equations, which are solved numerically on the basis of the finite volume method. The simulation is carried out for plates with different thicknesses and shapes of edges in a wide range of control parameters of the oscillatory process: dimensionless frequency and amplitude of oscillations. For the first time in the framework of one model all two-dimensional flow regimes, which were found earlier in experimental studies, are described. Two new flow regimes emerging along the stability boundaries of symmetric flow regimes are localized. The map of flow regimes in the frequency–amplitude plane is constructed. The analysis of the hydrodynamic influence of flows on the plates allow us to establish new effects associated with the influence of the shape of the plates on the drag and inertia forces. Due to these effects, the values of hydrodynamic forces can differ by 90 % at the same parameters of the oscillation. The lower and upper estimates of hydrodynamic forces obtained in the work have a good agreement with the experimental data presented in the literature.

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