Studies of Acoustic Characteristics and Their Comparison With Vibration Ones

Reciprocity Method ◽

Force Characteristics

Abstract The present paper gives the methods, schemes and results of experiments based on direct and reciprocal methods of measurements. The use of the reciprocity method made it possible to solve the problem of determining the acoustic characteristics of the distributed system model where vibroactive sources are represented in the form of passive models. It has been shown that the normalized transfer coefficient characterizing a link between force and acoustic fields has the same value both for the model and in nature (in case of their full similarity) that can be used: - to improve the methods of designing and technological manufacturing of models based on the comparison of normalized transfer coefficients obtained for full-scale and physical models; - to forecast the acoustic radiation of some vibroactive mechanisms using the assigned force characteristics and normalized transfer coefficients obtained for a model with the modelling scale taken into account.

Some Aspects of Acoustic Emissions during the Launch of a Space Rocket in Research of Earth by Satellites

10.5194/egusphere-egu21-15036 ◽

2021 ◽

Author(s):

Galyna Sokol ◽

Vladyslav Kotlov ◽

Victor Frolov ◽

Volodymyr Syrenko ◽

Volodymyr Dudnikov

Keyword(s):

Acoustic Radiation ◽

Acoustic Emissions ◽

Experimental Tests ◽

Acoustic Vibration ◽

Physical Models ◽

Acoustic Fields ◽

Acoustic Vibrations ◽

Secondary Sources ◽

Space Rocket ◽

Plates And Shells

Acoustic fields of various types of radiation and power arise during the rocket&#8217;s movement in the atmosphere after the launch. One of the most topical studies here is the analysis and assessment of the infrasonic radiation levels and their impact on the health of the nearby settlements population and the spaceport maintenance personnel. Therefore, it is necessary to identify the features and determine the directions of acoustic radiation research based on existing ideas about the generation, propagation, and impact of infrasound.The methodology for researching acoustic radiation during rocket movement includes identifying the primary sources of acoustic vibrations. That is vibrations from a working propulsion system, from the vibrating shell of the rocket case, turbulent vortices in the flow around the rocket case. And also the identification of acoustic vibrations secondary sources arising from the primary vibrations reflection from collisions with obstacles, for example, the launch pad surface type.It is necessary to develop physical models of acoustic fields, the nature of which depends primarily on the type of acoustic sources.These are the following models:<ul><li>point radiation (monopoles);</li> <li>analysis of acoustic fields generated in the environment by force acting on a rigid surface and characterized by the Lamb potential;</li> <li>acoustic radiation and fields during vibrations of plates and shells of various shapes, lengths, and areas;</li> <li>acoustic radiation during the movable environment and solid bodies interaction;</li> <li>acoustic radiation at the jets outflow from nozzles;</li> <li>excitation and propagation of acoustic vibrations inside gas and liquid cavities, taking into account the peculiarities of the shells&#8217; structural schemes, the resonances identification;</li> <li>monochromatic and pulsed radiation.</li> </ul>The next step is the creation of mathematical models designed to calculate the acoustic field characteristics (analytical methods, the use of Taylor and Fourier series, numerical programming methods). Mathematical dependences will make it possible to analyze the relationship between the acoustic radiation sources energy characteristics and the characteristics of their acoustic fields. It is important to calculate the acoustic radiation amplitude-frequency characteristics.Experimental tests, the development of programs, and methods for measuring the acoustic vibration characteristics are important. At the same time, a list of equipment necessary for measuring acoustic characteristics (instruments, circuits, equipment) is created.As a result of physical and mathematical analysis of acoustic vibrations sources, it is possible to develop active and passive methods of damping them. As well as giving recommendations for damping acoustic vibrations.

Systematic heat transfer measurements in highly viscous binary fluids

Heat and Mass Transfer ◽

10.1007/s00231-021-03087-w ◽

2021 ◽

Author(s):

Ann-Christin Fleer ◽

Markus Richter ◽

Roland Span

Keyword(s):

Heat Transfer ◽

Transfer Coefficient ◽

Volatile Component ◽

Test Tube ◽

Heat Fluxes ◽

Transfer Coefficients ◽

Low Viscosity ◽

The Heat Transfer Coefficient

AbstractInvestigations of flow boiling in highly viscous fluids show that heat transfer mechanisms in such fluids are different from those in fluids of low viscosity like refrigerants or water. To gain a better understanding, a modified standard apparatus was developed; it was specifically designed for fluids of high viscosity up to 1000 Pa∙s and enables heat transfer measurements with a single horizontal test tube over a wide range of heat fluxes. Here, we present measurements of the heat transfer coefficient at pool boiling conditions in highly viscous binary mixtures of three different polydimethylsiloxanes (PDMS) and n-pentane, which is the volatile component in the mixture. Systematic measurements were carried out to investigate pool boiling in mixtures with a focus on the temperature, the viscosity of the non-volatile component and the fraction of the volatile component on the heat transfer coefficient. Furthermore, copper test tubes with polished and sanded surfaces were used to evaluate the influence of the surface structure on the heat transfer coefficient. The results show that viscosity and composition of the mixture have the strongest effect on the heat transfer coefficient in highly viscous mixtures, whereby the viscosity of the mixture depends on the base viscosity of the used PDMS, on the concentration of n-pentane in the mixture, and on the temperature. For nucleate boiling, the influence of the surface structure of the test tube is less pronounced than observed in boiling experiments with pure fluids of low viscosity, but the relative enhancement of the heat transfer coefficient is still significant. In particular for mixtures with high concentrations of the volatile component and at high pool temperature, heat transfer coefficients increase with heat flux until they reach a maximum. At further increased heat fluxes the heat transfer coefficients decrease again. Observed temperature differences between heating surface and pool are much larger than for boiling fluids with low viscosity. Temperature differences up to 137 K (for a mixture containing 5% n-pentane by mass at a heat flux of 13.6 kW/m2) were measured.

Acoustic Characteristics of a Gas Turbine Exhaust Model

Journal of Engineering for Power ◽

10.1115/1.3445791 ◽

1974 ◽

Vol 96 (3) ◽

pp. 181-184 ◽

Cited By ~ 1

Author(s):

J. R. Cummins

Keyword(s):

Gas Turbine ◽

Acoustic Radiation ◽

Flow Path ◽

Scale Model ◽

Temperature Ratio ◽

Gas Turbine Exhaust ◽

Acoustical Data ◽

Turbine Exhaust

To investigate the sources of acoustic radiation from a gas turbine exhaust, a one-seventh scale model has been constructed. The model geometrically scales the flow path downstream of the rotating parts including support struts and turning vanes. A discussion and comparison of different kinds of aerodynamic and acoustic scaling techniques are given. The effect of the temperature ratio between model and prototype is found to be an important parameter in comparing acoustical data.

USE OF GROOVED SURFACES TO IMPROVE HYDRODYNAMIC, CAVITATION AND ACOUSTIC CHARACTERISTICS OF WINGS AND ELEMENTS OF VANE PROPULSION SYSTEMS (REVIEW)

Fundamental and Applied Problems of Engineering and Technology ◽

10.33979/2073-7408-2021-346-2-3-17 ◽

2021 ◽

Vol 2 ◽

pp. 3-17

Author(s):

A.L. SUKHORUKOV

Keyword(s):

Computational Models ◽

Acoustic Radiation ◽

Hydrodynamic Cavitation ◽

Propulsion Systems ◽

Flow Parameters ◽

Turbulent Transition ◽

Grooved Surface ◽

Propeller Blades ◽

Laminar Turbulent Transition

The paper reviews the use of grooved surfaces and sawtooth (chevron) edges to control the flow parameters of the wings, propeller blades and elements of vane propulsion systems operating in both gaseous and liquid media. Particular attention is paid to the physical mechanisms of improving the hydrodynamic, cavitation and acoustic characteristics under the influence of a grooved surface. These mechanisms are associated with a change in the flow structure in the region of the laminar-turbulent transition, the peculiarities of the occurrence of cavitation and acoustic radiation in the region of the outgoing edges. The results of the verification of computational models describing the behavior of the flow taking into account the laminar-turbulent transition, the use of which is necessary for studying flows near a grooved surface, are presented.

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

Experimental Study of Evaporation Heat Transfer Characteristics and Pressure Drops of R410A and R134a in a Multiport Mini-Channel

10.1115/icnmm2009-82209 ◽

2009 ◽

Cited By ~ 1

Author(s):

Jatuporn Kaew-On ◽

Somchai Wongwises

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Transfer Coefficient ◽

Transfer Coefficients ◽

Pressure Drops ◽

Evaporation Heat ◽

Evaporation Heat Transfer ◽

R 134A

The evaporation heat transfer coefficients and pressure drops of R-410A and R-134a flowing through a horizontal-aluminium rectangular multiport mini-channel having a hydraulic diameter of 3.48 mm are experimentally investigated. The test runs are done at refrigerant mass fluxes ranging between 200 and 400 kg/m2s. The heat fluxes are between 5 and 14.25 kW/m2, and refrigerant saturation temperatures are between 10 and 30 °C. The effects of the refrigerant vapour quality, mass flux, saturation temperature and imposed heat flux on the measured heat transfer coefficient and pressure drop are investigated. The experimental data show that in the same conditions, the heat transfer coefficients of R-410A are about 20–50% higher than those of R-134a, whereas the pressure drops of R-410A are around 50–100% lower than those of R-134a. The new correlations for the evaporation heat transfer coefficient and pressure drop of R-410A and R-134a in a multiport mini-channel are proposed for practical applications.

Calculation of Hourly Output of a Solar Still

Journal of Solar Energy Engineering ◽

10.1115/1.2930055 ◽

1993 ◽

Vol 115 (4) ◽

pp. 231-236 ◽

Cited By ~ 28

Author(s):

V. B. Sharma ◽

S. C. Mullick

Keyword(s):

Heat Transfer ◽

Transfer Coefficient ◽

Heat Balance ◽

Solar Still ◽

Balance Equations ◽

Transfer Coefficients ◽

Hourly Output ◽

The Heat Balance

An approximate method for calculation of the hourly output of a solar still over a 24-hour cycle has been studied. The hourly performance of a solar still is predicted given the values of the insolation, ambient temperature, wind heat-transfer coefficient, water depth, and the heat-transfer coefficient through base and sides. The proposed method does not require graphical constructions and does not assume constant heat-transfer coefficients as in the previous methods. The possibility of using the values of the heat-transfer coefficients for the preceding time interval in the heat balance equations is examined. In fact, two variants of the basic method of calculation are examined. The hourly rate of evaporation is obtained. The results are compared to those obtained by numerical solution of the complete set of heat balance equations. The errors from the approximate method in prediction of the 24-hour output are within ±1.5 percent of the values from the numerical solution using the heat balance equations. The range of variables covered is 5 to 15 cms in water depth, 0 to 3 W/m2K in a heat-transfer coefficient through base and sides, and 5 to 40 W/m2K in a wind heat-transfer coefficient.

The Measurement of Full-Surface Internal Heat Transfer Coefficients for Turbine Airfoils Using a Non-Destructive Thermal Inertia Technique

Volume 3: Turbo Expo 2002, Parts A and B ◽

10.1115/gt2002-30199 ◽

2002 ◽

Cited By ~ 2

Author(s):

Nirm V. Nirmalan ◽

Ronald S. Bunker ◽

Carl R. Hedlung

Keyword(s):

Heat Transfer ◽

Transfer Coefficient ◽

External Surface ◽

Internal Heat ◽

Transfer Coefficients ◽

Turbine Airfoils ◽

Non Destructive ◽

Internal Heat Transfer

A new method has been developed and demonstrated for the non-destructive, quantitative assessment of internal heat transfer coefficient distributions of cooled metallic turbine airfoils. The technique employs the acquisition of full-surface external surface temperature data in response to a thermal transient induced by internal heating/cooling, in conjunction with knowledge of the part wall thickness and geometry, material properties, and internal fluid temperatures. An imaging Infrared camera system is used to record the complete time history of the external surface temperature response during a transient initiated by the introduction of a convecting fluid through the cooling circuit of the part. The transient data obtained is combined with the cooling fluid network model to provide the boundary conditions for a finite element model representing the complete part geometry. A simple 1D lumped thermal capacitance model for each local wall position is used to provide a first estimate of the internal surface heat transfer coefficient distribution. A 3D inverse transient conduction model of the part is then executed with updated internal heat transfer coefficients until convergence is reached with the experimentally measured external wall temperatures as a function of time. This new technique makes possible the accurate quantification of full-surface internal heat transfer coefficient distributions for prototype and production metallic airfoils in a totally non-destructive and non-intrusive manner. The technique is equally applicable to other material types and other cooled/heated components.

THE STUDY OF ACOUSTIC CHARACTERISTICS OF THE PERFORATED AND HOMOGENOUS PLATES WITH SIMILAR GEOMETRICAL DIMENSIONS

Akustika ◽

10.36336/akustika20193279 ◽

2019 ◽

Vol 32 ◽

pp. 79-82

Author(s):

Valery Kirpichnikov ◽

Lyudmila Drozdova ◽

Alexei Koscheev ◽

Ernst Myshinsky

Keyword(s):

Resonant Frequency ◽

Acoustic Radiation ◽

Perforated Plate ◽

Resonant Frequencies ◽

Perforated Plates ◽

Resonance Frequencies ◽

Flexural Vibrations ◽

Geometrical Dimensions

The resonance frequencies of the flexural vibrations, input vibration excitability and acoustic radiation of the homogeneous and perforated plates were investigated. It is established that the average reduction range of the lower resonant frequency of flexural vibrations of the tested plates with the holes virtually coincides with the predictive estimate. The levels of the input vibration excitability of the perforated plate at the lower resonant frequencies exceeded the levels at the corresponding frequencies of the homogeneous plates greater than the calculated value. The levels of resonance acoustic radiation of the perforated plate were significantly less than of the homogeneous one.

FORCED CONVECTION DRYING OF INDIAN GROUNDNUT: AN EXPERIMENTAL STUDY

Facta Universitatis Series Mechanical Engineering ◽

10.22190/fume160812011s ◽

2017 ◽

Vol 15 (3) ◽

pp. 467

Author(s):

Ravinder Kumar Sahdev ◽

Mahesh Kumar ◽

Ashwani Kumar Dhingra

Keyword(s):

Heat Transfer ◽

Transfer Coefficient ◽

Forced Convection ◽

Experimental Error ◽

Linear Regression Analysis ◽

Convective Heat Transfer Coefficient ◽

Transfer Coefficients ◽

Evaporative Heat Transfer

In this paper, convective and evaporative heat transfer coefficients of the Indian groundnut were computed under indoor forced convection drying (IFCD) mode. The groundnuts were dried as a single thin layer with the help of a laboratory dryer till the optimum safe moisture storage level of 8 – 10%. The experimental data were used to determine the values of experimental constants C and n in the Nusselt number expression by a simple linear regression analysis and consequently, the convective heat transfer coefficient (CHTC) was determined. The values of CHTC were used to calculate the evaporative heat transfer coefficient (EHTC). The average values of CHTC and EHTC were found to be 2.48 W/m2 oC and 35.08 W/m2 oC, respectively. The experimental error in terms of percent uncertainty was also estimated. The experimental error in terms of percent uncertainty was found to be 42.55%. The error bars for convective and evaporative heat transfer coefficients are also shown for the groundnut drying under IFCD condition.

Film Cooling Downstream of a Row of Discrete Holes With Compound Angle

Journal of Turbomachinery ◽

10.1115/1.1344905 ◽

2000 ◽

Vol 123 (2) ◽

pp. 222-230 ◽

Cited By ~ 48

Author(s):

R. J. Goldstein ◽

P. Jin

Keyword(s):

Mass Transfer ◽

Transfer Coefficient ◽

Mass Transfer Coefficient ◽

Film Cooling ◽

Transfer Coefficients ◽

Cooling Effectiveness ◽

Mass Transfer Coefficients ◽

Cooling Performance ◽

Film Cooling Effectiveness ◽

Compound Angle

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35 deg inclination angle and 45 deg compound angle with 3d hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetric vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.