Experimental Analysis of a Waveguide Pressure Measuring System

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Matthew A. White ◽  
Manuj Dhingra ◽  
J. V. R. Prasad
Keyword(s):  
Theoretical Model ◽  
Measuring System ◽  
Pressure Waves ◽  
Unique Contribution ◽  
Pressure Oscillations ◽  
Fluctuating Pressure ◽  
Response Data ◽  
Theoretical Predictions ◽  
Infinite Line ◽  
M 12

An infinite-line probe is commonly used to measure unsteady pressure in high-temperature environments while protecting the pressure transducer. In this study, an existing theoretical model is used to derive the response of a waveguide pressure measuring system. An ambient temperature centrifugal compressor rig acts as an experimental source of fluctuating pressure. The compressor is operated at different discrete rotational speeds, and the blade-passing frequencies are used to obtain frequency response data. In the experiments, pressure waves attenuated at a rate faster than that predicted by the theoretical model for a 0.322 m (12 in.) sensor offset. Furthermore, the decay in the magnitude of the pressure oscillations accelerated at blade-passing frequencies above 9 kHz. A unique contribution of this study is to show that whereas the experimentally observed overall attenuation is broadly consistent with the theoretical predictions, pressure oscillations corresponding to individual blade passages may be disproportionally attenuated.

Experimental Analysis of a Waveguide Pressure Measuring System

2009 ◽  
Author(s):  
Matthew A. White ◽  
Manuj Dhingra ◽  
J. V. R. Prasad
Keyword(s):  
Theoretical Model ◽  
Measuring System ◽  
Pressure Waves ◽  
Unique Contribution ◽  
Pressure Oscillations ◽  
Fluctuating Pressure ◽  
Response Data ◽  
Theoretical Predictions ◽  
Infinite Line ◽  
M 12

An infinite line probe is commonly used to measure unsteady pressure in high temperature environments while protecting the pressure transducer. In this study, an existing theoretical model is used to derive the response of a waveguide pressure measuring system. An ambient temperature centrifugal compressor rig acts as an experimental source of fluctuating pressure. The compressor is operated at different discrete rotational speeds, and the blade passing frequencies are used to obtain frequency response data. In the experiments, pressure waves attenuated at a rate faster than that predicted by the theoretical model for a 0.322 m (12 in) sensor offset. Further, the decay in the magnitude of the pressure oscillations accelerated at blade passing frequencies above 9 kHz. A unique contribution of this study is to show that whereas the experimentally observed overall attenuation is broadly consistent with the theoretical predictions, pressure oscillations corresponding to individual blade passages may be disproportionally attenuated.

scholarly journals Consumption Responses to In-Kind Transfers: Evidence from the Introduction of the Food Stamp Program

2009 ◽  
Vol 1 (4) ◽  
pp. 109-139 ◽  
Author(s):  
Hilary W Hoynes ◽  
Diane Whitmore Schanzenbach
Keyword(s):  
Theoretical Model ◽  
Empirical Work ◽  
Food Stamps ◽  
Cash Income ◽  
Food Stamp Program ◽  
Difference In Difference ◽  
Food Expenditures ◽  
Theoretical Predictions ◽  
Difference Methods ◽  
The Impact

Economists have strong theoretical predictions about how in-kind transfers, such as providing vouchers for food, impact consumption. Despite the prominence of the theory, there is little empirical work on responses to in-kind transfers, and most existing work fails to support the canonical theoretical model. We employ difference-in-difference methods to estimate the impact of program introduction on food spending. Consistent with predictions, we find that food stamps reduce out-of-pocket food spending and increase overall food expenditures. We also find that households are inframarginal and respond similarly to one dollar in cash income and one dollar in food stamps. (JEL D12, H23, I38)

A clinical study which relates to a theoretical simulation of the glucose transport in the human placenta under various diabetic conditions

2016 ◽  
Vol 44 (4) ◽  
Author(s):  
Efrath Barta ◽  
Arieh Drugan
Keyword(s):  
Clinical Study ◽  
Theoretical Model ◽  
Gestational Diabetes ◽  
Human Placenta ◽  
Major Effect ◽  
Fetal Weight ◽  
Blood Levels ◽  
Theoretical Simulation ◽  
Theoretical Predictions ◽  
Glucose Supply

AbstractTo characterize placental glucose delivery under normoglycemic conditions, gestational and pre-gestational diabetes and to relate the clinical data to theoretical predictions.Data from 125 pregnancies: 50 normal gestations and 75 ones with various types of diabetes were collected. In parallel, we formulated a theoretical model for the transport of glucose under various diabetic conditions. Measured glucose blood levels were fed into the theoretical model that predicts glucose supply to the fetus and the results were confronted with measured fetal weights.Measured fetal weight and computed glucose delivery in gestational diabetic parturients resemble the situation in normal pregnancies. However, pre-gestational diabetes has a major effect as it involves heavier fetuses and enhanced computed glucose fluxesFetal weight (increased in pre-gestational and unaltered in gestational diabetes) correlates with the predicted rate of glucose delivery through the placenta.

Chasing Diamonds and Crowns: Consumer Limited Attention and Seller Response

2021 ◽  
Author(s):  
Zemin (Zachary) Zhong
Keyword(s):  
Theoretical Model ◽  
Regression Discontinuity ◽  
Limited Attention ◽  
Supply Side ◽  
Demand Side ◽  
Demand Shock ◽  
Online Platforms ◽  
Theoretical Predictions ◽  
Shaped Pattern ◽  
Sales Increase

Online platforms often assign sellers summary symbols based on whether their ratings pass certain thresholds. Consumers may focus on the symbols and pay limited attention to the ratings. This bias leads to discontinuously increased demand at the thresholds. I use a theoretical model to illustrate that sellers will lower the prices before their ratings reach the thresholds and increase their prices afterward due to the positive demand shock. I collect data from Taobao to test the theoretical predictions. Using regression discontinuity, I find that on the demand side, the hourly sales increase significantly when a seller passes the threshold, even conditional on the same item. On the supply side, the prices indeed exhibit a V-shaped pattern with respect to the ratings. Furthermore, sellers preemptively increase prices shortly before reaching thresholds, supporting the theoretical predictions. This paper was accepted by Juanjuan Zhang, marketing.

scholarly journals Estimation of Squeeze-Film Damping and Inertial Coefficients from Experimental Free-Decay Data

1986 ◽  
Vol 200 (2) ◽  
pp. 123-133 ◽  
Author(s):  
J B Roberts ◽  
R Holmes ◽  
P J Mason
Keyword(s):  
Linear Model ◽  
Transient Response ◽  
Parametric Identification ◽  
Squeeze Film ◽  
Decay Data ◽  
Operating Range ◽  
Response Data ◽  
Squeeze Film Damping ◽  
Free Decay ◽  
Theoretical Predictions

This paper describes the results obtained from an experimental programme concerned with a parametric identification of the damping and inertial coefficients of a cylindrical squeeze-film bearing, through an analysis of transient response data. The results enable the operating range for which a linear model of the squeeze-film is appropriate to be determined. Comparisons are made between the estimated coefficients and theoretical predictions.

The elastochrone: the descent time of a sphere on a flexible beam

2009 ◽  
Vol 465 (2107) ◽  
pp. 2293-2311 ◽  
Author(s):  
Jeffrey M. Aristoff ◽  
Christophe Clanet ◽  
John W.M. Bush
Keyword(s):  
Gravitational Field ◽  
Theoretical Model ◽  
Elastic Beam ◽  
Beam Theory ◽  
Flexible Beam ◽  
Bernoulli Beam ◽  
Horizontal Beam ◽  
Theoretical Predictions ◽  
Static Regime ◽  
Euler Bernoulli Beam

We present the results of a combined experimental and theoretical investigation of the motion of a sphere on an inclined flexible beam. A theoretical model based on Euler–Bernoulli beam theory is developed to describe the dynamics, and in the limit where the beam reacts instantaneously to the loading, we obtain exact solutions for the load trajectory and descent time. For the case of an initially horizontal beam, we calculate the period of the resulting oscillations. Theoretical predictions compare favourably with our experimental observations in this quasi-static regime. The time taken for descent along an elastic beam, the elastochrone, is shown to exceed the classical brachistochrone, the shortest time between two points in a gravitational field.

Fuel Injection Scheme for a Compact Afterburner Without Flameholders

2007 ◽  
Author(s):  
Shai Birmaher ◽  
Philipp W. Zeller ◽  
Peter Wirfalt ◽  
Yedidia Neumeier ◽  
Ben T. Zinn
Keyword(s):  
Theoretical Model ◽  
Gas Turbine ◽  
Fuel Injection ◽  
State Of The Art ◽  
Combustion Process ◽  
Operating Conditions ◽  
Experimental Setup ◽  
Turbine Engine ◽  
Theoretical Predictions ◽  
Significant Length

State of the art afterburner combustion employs spray bars and flameholders in a long cavity, which adds significant length and weight to the engine and increases its observability. This paper presents a feasibility study for the development of a compact “prime and trigger” afterburner that eliminates the flameholders and reduces the length of the engine. In this concept, fuel is injected just upstream or in between the turbine stages in such a manner that upon exiting the turbine the fuel has evaporated and premixed with the flow without significant combustion, a process referred to as “priming”. Downstream of the turbine, combustion is initiated either through autoignition or by using a low power plasma radical generator being developed in a parallel investigation to “trigger” the combustion process. The prime and trigger injection and ignition scheme has been investigated using an experimental setup that simulates the operating conditions in a typical gas turbine engine. For this investigation, a trigger is not used, and combustion of the fuel occurs through autoignition. A physics-based theoretical model was developed to predict the location of autoignition for given flow and spray properties and injection locations. The theoretical predictions and the experimental results obtained using thermocouple measurements and CH* chemiluminescence confirm the feasibility of the prime and trigger concept by demonstrating the predictable and controlled autoignition of the afterburner fuel.

An Investigation Into Quantifying Pressure Wave Oscillation in the Lung

2010 ◽  
Author(s):  
J. Mussa ◽  
A. M. Al-Jumaily ◽  
G. Ijpma
Keyword(s):  
Wave Propagation ◽  
Medical Devices ◽  
Pressure Wave ◽  
Pressure Oscillation ◽  
Variable Pressure ◽  
Pressure Waves ◽  
Pressure Oscillations ◽  
Wave Oscillation ◽  
Airway Tree

Understanding pressure wave propagation in the lung is of importance for a number of medical devices including those for diagnostics and treatments. The main objective of this research is to quantify the transmitability of the airway tree with respect to pressure oscillations. Ovine lungs are casted to produce a hollow airway tree. Variable pressure oscillations and airflow are supplied at the trachea of the casted model and pressure oscillations are measured at the bronchioles. The study indicates that pressure waves with different frequencies can be delivered to different locations of the lung by controlling the pressure oscillation source to the lung.

A Theoretical and Experimental Investigation of a Gas-Operated Bearing Damper for Turbomachinery: Part I—Theoretical Model and Predictions

1995 ◽  
Vol 117 (4) ◽  
pp. 742-749 ◽  
Author(s):  
P. Sundararajan ◽  
J. M. Vance
Keyword(s):  
Theoretical Model ◽  
Squeeze Film ◽  
Working Fluid ◽  
Previous Theory ◽  
Damping Characteristics ◽  
Squirrel Cage ◽  
Theoretical Predictions ◽  
Current Design ◽  
Gas Damper ◽  
Hardware Designs

This is the first (Part I) of two papers describing recent results of the research program directed at developing a vibration damper suitable for high-temperature turbomachinery applications. It is expected that such dampers will replace squeeze-film dampers, which use oil as the working fluid and have limitations at higher temperatures. A novel gas-operated bearing damper has been evaluated analytically and experimentally for its damping characteristics. A theory based on the isentropic assumptions predicts the damper performance characteristics reasonably well. A maximum damping level of 2311 N-m/s (13.2 lb-s/in.) at a frequency of 100 Hz was measured with a single actuator of the gas damper. Since many such actuators could be placed circumferentially around the squirrel cage, considerable damping levels can be realized. The study also shows that significantly higher damping levels can be achieved by modifying the current design. Part I describes the theoretical model that has been developed based on isentropic assumptions. This model is an improved version of the previous theory (Vance et al., 1991) and includes the supply groove effects, dynamic area changes of the inlet feeding holes, and the effects of flow choking on damper behavior. The governing equations are derived and theoretical predictions using these equations have been made for two hardware designs that were experimentally investigated (see Part II for experimental results).

scholarly journals REINFORCED AND PRESTRESSED CONCRETE HOLLOW BEAMS UNDER TORSION

2014 ◽  
Vol 19 (Supplement_1) ◽  
pp. S141-S152 ◽  
Author(s):  
Luis F. A. Bernardo ◽  
Jorge M. A. Andrade ◽  
Luiz A. Pereira-De-Oliveira
Keyword(s):  
Theoretical Model ◽  
Prestressed Concrete ◽  
Experimental Results ◽  
Membrane Model ◽  
Global Behaviour ◽  
Theoretical Predictions ◽  
Hollow Beams

Recently a new rational theoretical model for beams under torsion has been proposed. This model, called Softened Membrane Model for Torsion (SMMT), is able to predict well the global behaviour of reinforced and prestressed concrete solid beams under torsion. This paper presents a study in order to check the SMMT for reinforced and prestressed concrete hollow beams under torsion. Theoretical predictions from SMMT are compared to some experimental results of hollow beams available in the literature and also with the predictions of another theoretical model previously proposed from the authors. It is shown that SMMT, with some corrections, is able to predict satisfactorily the overall behaviour of reinforced and prestressed concrete hollow beams under torsion.

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