Pressure loss mechanism analysed with pipe turbulence theory and friction coefficient prediction in labyrinth path of drip irrigation emitter

In this work, unsteady viscous flow analysis around turbine blade cascade using a High-Order LES turbulent model is carried out to investigate basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in our work, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. Our study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end-wall, downstream the trailing edge resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.

Download Full-text

Using TDR to Estimate Water Application Efficiency for Drip Irrigation Emitter Patterns on Banana

10.13031/2013.29872 ◽

2010 ◽

Author(s):

Alisson J. P da Silva ◽

Eugênio F Coelho ◽

Jarbas H de Miranda

Keyword(s):

Drip Irrigation ◽

Water Application ◽

Application Efficiency ◽

Water Application Efficiency ◽

Drip Irrigation Emitter

Download Full-text

Accurate Estimation of Profile Losses and Analysis of Loss Generation Mechanisms in a Turbine Cascade

Journal of Turbomachinery ◽

10.1115/1.4037858 ◽

2017 ◽

Vol 139 (12) ◽

Cited By ~ 12

Author(s):

D. Lengani ◽

D. Simoni ◽

M. Ubaldi ◽

P. Zunino ◽

F. Bertini ◽

...

Keyword(s):

Boundary Layer ◽

Pressure Loss ◽

Total Pressure ◽

Loss Coefficient ◽

Total Pressure Loss ◽

Accurate Estimation ◽

Loss Mechanism ◽

Pressure Loss Coefficient ◽

Generation Mechanisms ◽

Total Pressure Loss Coefficient

The paper analyzes losses and the loss generation mechanisms in a low-pressure turbine (LPT) cascade by proper orthogonal decomposition (POD) applied to measurements. Total pressure probes and time-resolved particle image velocimetry (TR-PIV) are used to determine the flow field and performance of the blade with steady and unsteady inflow conditions varying the flow incidence. The total pressure loss coefficient is computed by traversing two Kiel probes upstream and downstream of the cascade simultaneously. This procedure allows a very accurate estimation of the total pressure loss coefficient also in the potential flow region affected by incoming wake migration. The TR-PIV investigation concentrates on the aft portion of the suction side boundary layer downstream of peak suction. In this adverse pressure gradient region, the interaction between the wake and the boundary layer is the strongest, and it leads to the largest deviation from a steady loss mechanism. POD applied to this portion of the domain provides a statistical representation of the flow oscillations by splitting the effects induced by the different dynamics. The paper also describes how POD can dissect the loss generation mechanisms by separating the contributions to the Reynolds stress tensor from the different modes. The steady condition loss generation, driven by boundary layer streaks and separation, is augmented in the presence of incoming wakes by the wake–boundary layer interaction and by the wake dilation mechanism. Wake migration losses have been found to be almost insensitive to incidence variation between nominal and negative (up to −9 deg) while at positive incidence, the losses have a steep increase due to the alteration of the wake path induced by the different loading distribution.

Download Full-text

Studies on Unsteady Flow Characteristics in a High Pressure Turbine Cascade Based on a High-Order Large Eddy Simulation Turbulence Model

Journal of Turbomachinery ◽

10.1115/1.4003974 ◽

2012 ◽

Vol 134 (5) ◽

Cited By ~ 2

Author(s):

Tomohiko Jimbo ◽

Debasish Biswas ◽

Yoshiki Niizeki

Keyword(s):

Turbulence Model ◽

Physical Process ◽

Pressure Loss ◽

Flow Behavior ◽

Flow Analysis ◽

Three Dimensional ◽

Flow Characteristics ◽

Measured Data ◽

High Order ◽

Loss Mechanism

In the present paper, unsteady viscous flow analysis around turbine blade cascade using a high-order LES turbulence model is carried out to investigate the basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in the present paper, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. The present study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end wall, downstream of the trailing edge, resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.

Download Full-text