Constant-temperature Hot-wire Anemometer Research Articles

Experimental validation on a calibration position of a hot-wire anemometer for measuring multi-scale grid-generated turbulence

This study aims to experimentally examine conditions that should be satisfied by a calibration position of a constant-temperature hot-wire anemometer. Specifically, this study addresses an appropriate measurement point when this calibration is performed downstream of a turbulent field generated by a multi-scale turbulence grid. The hot-wire measurement in this study is based on an I-type probe with a standard 5 μm tungsten wire. The hot-wire anemometer in this study is small and can be attached to a probe support. In this study, uncertainty in the calibration curve of the hot-wire measurement is first checked. Here, Pitot tube velocimetry to obtain the calibration curves is carried out using two bell-type micro-differential pressure gauges. Then, the characteristics of the obtained velocity fluctuations and turbulence will be examined. Based on this relative velocity fluctuation RMS value, the effects of the obtained streamwise velocity fluctuation on output voltage are obtained by asymptotically expanding a calibration curve. Using these results, the intensity of the free-stream turbulence, which has a negligible effect on output voltage giving a calibration curve, is clarified.

FLOW STRUCTURES IN THE WAKE REGION OF TWO INCLINED FLAT PLATES IN A SYMMETRICAL TANDEM ARRANGEMENT

Flow properties and wake structures behind bluff bodies have fascinated many researchers for years. Such interest in this phenomenon is due to various applications of bluff bodies in engineering and industry. In this study, flow structures and the downstream wake behind two inclined flat plates in a symmetrical tandem arrangement have been studied experimentally at Reynolds number of 23,000. Constant-temperature hot wire anemometers (CTAs) were employed to quantitatively measure the near wake properties in terms of shedding frequency, velocity components, and turbulent kinetic energy (TKE). The effects of gap ratio (<i>g/D</i>) between the plates and the angle of attack (α) on the wake flow structure have been probed in detail quantitatively. It was found that for a given gap ratio <i>g/D</i>, the Strouhal number decreases as the angle of attack increases. Moreover, for a given angle of attack a, the Strouhal number increases as the gap ratio <i>g/D</i> increases. Interestingly, it was observed that for a given gap ratio <i>g/D</i>, the coherent TKE peak production decreases as the angle of attack increases.

FLOW STRUCTURES IN THE WAKE REGION OF AN L-SHAPED CYLINDER AND A TRIANGULAR CYLINDER

Researchers have been intrigued by the flow properties and wake structures behind bluff bodies for years, driven by the varied applications of these bodies in engineering and industry. In this study, flow structures and the downstream wake behind a triangular cylinder (TC) and an L-shaped cylinder (LSC) have been studied experimentally at Reynolds number of 18,100. Constant-temperature hot-wire anemometers were employed to quantitatively measure the near wake properties in terms of velocity components and turbulent kinetic energy (TKE), and similarities and dissimilarities in coherent structure have been addressed in detail quantitatively for the first time. It was found that the wake region behind the LSC exhibits a delay in wake recovery in comparison to the TC. In other words, the dominant status of the vortex shedding phenomena occurs at a higher x/D for LSC in comparison to the TC. The coherent TKE peak of an LSC is about 22% lower than the coherent TKE peak of the TC in the near wake region while on average it is about 20% higher in the far wake region. Finally, it was found that the maximum coherent TKE peak of LSCs occurs at a larger x/D ratio, which can be concluded as an indication of a location delay in the wake region in comparison with the TC case.

A Thermal Anemometry Method for Studying the Unsteady Gas Dynamics of Pipe Flows: Development, Modernisation, and Application.

A detailed study of the gas-dynamic behaviour of both liquid and gas flows is urgently required for a variety of technical and process design applications. This article provides an overview of the application and an improvement to thermal anemometry methods and tools. The principle and advantages of a hot-wire anemometer operating according to the constant-temperature method are described. An original electronic circuit for a constant-temperature hot-wire anemometer with a filament protection unit is proposed for measuring the instantaneous velocity values of both stationary and pulsating gas flows in pipelines. The filament protection unit increases the measuring system's reliability. The designs of the hot-wire anemometer and filament sensor are described. Based on development tests, the correct functioning of the measuring system was confirmed, and the main technical specifications (the time constant and calibration curve) were determined. A measuring system for determining instantaneous gas flow velocity values with a time constant from 0.5 to 3.0 ms and a relative uncertainty of 5.1% is proposed. Based on pilot studies of stationary and pulsating gas flows in different gas-dynamic systems (a straight pipeline, a curved channel, a system with a poppet valve or a damper, and the external influence on the flow), the applications of the hot-wire anemometer and sensor are identified.

Hot-Wire Anemometry in High Subsonic Organic Vapor Flows

AbstractThe present contribution reports the outcome of an experimental and numerical investigation of the behavior of a constant-temperature hot-wire anemometer in the high-subsonic flow up to a Mach number of 0.7 of the organic vapor Novec™ 649 at pressure and temperature levels of typical organic Rankine cycle (ORC) turbine applications. The experiments were carried out in the calibration section of a closed-loop organic vapor wind tunnel test facility enabling the independent variation of Reynolds numbers, Mach numbers, and total temperature within a certain range. It was found that the calibration and the determination of the sensitivity coefficients can be done in a way as proposed by de Souza and Tavoularis for air. The sensitivity coefficients for velocity and density were essentially equal for higher overheat ratios which support the interpretation of the signals and data reduction for turbulent quantities. Computational fluid dynamics (CFD) provided additional insight into potential real gas effects for hot-wire performance.

Physical simulation of aerodynamic flow characteristics in a vertical diffuser with air supply through different pipe configurations

RELEVANCE. Vertical cone diffusers are used in various technical applications: heat exchangers, gas cleaning units, boilers, industrial furnaces, dryers, ventilation devices, nozzle systems and others. For their efficient operation, it is necessary to ensure a uniform supply of the working medium to the device, which is determined by the characteristics of the flow in thediffuser. Thus, the study of the aerodynamics of technological devices with conical diffusers is an urgent task for gas-dynamic improvement and the search for ways to control flow characteristics. THE PURPOSE. To establish the evolution of the velocity field along the height of the cylindrical part of the diffuser for different configurations of the supply tubes, and also to determine the magnitude of the change in the intensity of turbulence along the height of the diffuser under different initial conditions based on experimental data on the instantaneous values of the air flow velocity. METHODS. Measurement of instantaneous values of air flow velocity is carried out using a constant temperature hot-wire anemometer. The article provides data on velocity fields and turbulence intensity along the height and along the diameter of the cylindrical part of the diffuser when air is supplied through tubes of different configurations. Feed tubes with cross sections in the form of a circle, a square and an equilateral triangle were used. RESULTS. The article provides a detailed description of the experimental stand (including key geometric dimensions), instrumentation and measurement system, and data processing techniques. The ranges of changes in the initial conditions for the experiments are presented. A comparison of the aeromechanical characteristics of flows in a vertical diffuser when air issupplied through different tube configurations is carried out. CONCLUSION. It is shown that in the diffuser there is a drop in the average velocity upstream, which is typical for all configurations of the supply tubes. It has been established that profiled tubes influence the shape of the velocity field. It was found that the values of turbulence intensity vary from 0.05 to 0.39 (the highest values were typical when air was supplied through profiled tubes). It is shown that the intensity of turbulence has its maximum values at a height of 300-350 mm, which is typical for all investigated tube configurations.

Effect of Small Angles of Attack on Turbulence Generation in Supersonic Boundary Layers on Swept Wings

We present the new (for Mach numbers М = 3 and 3.5) and generalizing (for Mach numbers from 2 to 4) results of experimental investigations on the effect of small angles of attack on laminar-turbulent transition in the supersonic boundary layer on a swept wing with the leading-edge slip angle of 72°. The angle-of-attack variation has a strong effect on the transition Reynolds number. The transition Reynolds number decreases with increase in the Mach number. The measurements were carried out by means of a constant-temperature hot-wire anemometer using the proven procedure of determining the transition location. The eN method is used for the first time for numerically estimating the transition Reynolds numbers in the supersonic boundary layer on a swept wing with the leading-edge slip angle of 72°. The growth of the amplitudes of the steady and unsteady modes of the boundary layer crossflow are calculated in accordance with the linear stability theory, within the framework of the Lees–Lin system of equations. The numerical results indicate that, in accordance with the experimental results, laminar-turbulent transition in the boundary layer on the model swept wing is governed by the growth of stationary modes of the crossflow instability.

Effect of Small Angles of Attack on Turbulence Generation in Supersonic Boundary Layers on Swept Wings

We present the new (for Mach numbers М = 3 and 3.5) and generalizing (for Mach numbers from 2 to 4) results of experimental investigations on the effect of small angles of attack on laminar-turbulent transition in the supersonic boundary layer on a swept wing with the leading-edge slip angle of 72°. The angle-of-attack variation has a strong effect on the transition Reynolds number. The transition Reynolds number decreases with increase in the Mach number. The measurements were carried out by means of a constant-temperature hot-wire anemometer using the proven procedure of determining the transition location. The eN method is used for the first time for numerically estimating the transition Reynolds numbers in the supersonic boundary layer on a swept wing with the leading-edge slip angle of 72°. The growth of the amplitudes of the steady and unsteady modes of the boundary layer crossflow are calculated in accordance with the linear stability theory, within the framework of the Lees–Lin system of equations. The numerical results indicate that, in accordance with the experimental results, laminar-turbulent transition in the boundary layer on the model swept wing is governed by the growth of stationary modes of the crossflow instability.

Mathematical Description of the Aerodynamic Characteristics of Stationary Flows in a Vertical Conical Diffuser When Air Is Supplied through Various Tube Configurations

Conical diffusers of various configurations are used in many kinds of technical equipment and manufacturing processes. Therefore, it is a relevant objective to obtain reliable experimental and mathematical data on the aerodynamic characteristics of diffusers. This article presents experimental data on the aerodynamics of stationary flows in a vertical conical diffuser when air is supplied through tubes with various cross sections (circle, square, and triangle). Instantaneous values of air flow velocity are measured with a constant-temperature hot-wire anemometer. Data are obtained on the velocity fields and turbulence intensity along the height and the diameter of the diffuser’s cylindrical part when air is supplied through tubes of various configurations. It is established that air supply through profiled tubes has a significant effect on the shape of the velocity field and turbulence intensity in a vertical conical diffuser. For example, higher values of turbulence intensity are typical of air supplied through profiled tubes (the differences reach 50%). A mathematical formulation (linear and exponential equations) of the change in the average speed and intensity of air flow turbulence along the height of the diffuser’s cylindrical part for various initial conditions and supply tube configurations is presented. The obtained findings will make it possible to refine mathematical models and update algorithms for engineering the design of diffusers for various engineering processes and pieces of technical equipment.

Stationary Gas Dynamics and Heat Transfer of Turbulent Flows in Straight Pipes at Different Turbulence Intensity

The gas-dynamic and heat-exchange behaviours of air flows in gas-dynamic systems have a significant impact on the efficiency and environmental performance of most technical equipment (heat engines, power plants, heat exchangers, etc.). Therefore, it is a relevant task to obtain reliable experimental data and physical laws on the influence of cross-sectional shape and initial turbulence intensity on gas dynamics and the level of heat transfer. In this study, data were experimentally obtained on the instantaneous values of the local velocity and local heat transfer coefficients of stationary air flows in straight pipes with circular, square, and triangular cross-sections at different initial values of the turbulence intensity. The measurements were carried out with a constant temperature hot-wire anemometer, thermocouples, and pressure sensors. Based on the research results, data on the turbulence intensity and averaged local heat transfer along the length of pipes with different cross-sections were summarised. It has been established that turbulence intensity in a square pipe is up to 40% higher than in a round channel; in a triangular channel, on the contrary, it is up to 28% lower. After the air flow’s initial turbulence, the relaxation of the flow in square and triangular pipes occurs faster than in a round channel. It is found that the initial intensity of turbulence leads to an increase in the averaged local heat transfer, which is typical of all investigated pipe configurations and initial conditions.

Experimental study of effect of a pair of weak shock waves on laminar-turbulent transition in the boundary layer of flat plate at Mach number 2

An experimental study of the effect of longitudinal vortices generated by weak shock waves on the laminar-turbulent transition in the boundary layer of a flat plate at a Mach number 2 is conducted. To amplify the effect of the longitudinal vortices generation, a model with leading edge blunting radius of 0,5 mm was used. The disturbance intensity was measured with a constant temperature hotwire anemometer and a single-wire sensor. To change the Reynolds numbers in the flow, the method of varying the pressure in the pretest section of a supersonic wind tunnel was used. According to the experimental conditions, the level of mass flow perturbations in the test section T325 of ITAM SB RAS did not exceed 0,1 % of the mean flow in the frequency range from 0,2 to 50 kHz. In this work, it is obtained for the first time that stationary streamwise vortices that arise in the boundary layer of a flat plate because of the action of a pair of weak shock waves on its leading edge lead to an early laminar-turbulent transition at different Reynolds numbers. In the case of a homogeneous boundary layer, the transition is achieved at Rex≈ 3,1 × 106, and in measurements in the region of vortices from shock waves at Rex≈ 1,5 × 106and Rex≈ 2 × 106.

An Indirect Method for Determining the Local Heat Transfer Coefficient of Gas Flows in Pipelines.

An indirect method and procedure for determining the local heat transfer coefficient in experimental studies on the intensity of heat transfer at a gas–surface interface is described. The article provides an overview of modern approaches and technical devices for determining the heat flux or friction stresses on surfaces in the study of thermophysical processes. The proposed method uses a constant-temperature hot-wire anemometer and a sensor with a thread sensitive element fixed on the surface of a fluoroplastic substrate. A substrate with the sensor’s sensitive element was mounted flush with the wall of the investigated pipeline. This method is based on the Kutateladze–Leontiev approach (the laws of friction and heat transfer) and the hydrodynamic analogy of heat transfer (the Reynolds analogy): this is an assumption about the unity of momentum and heat transfer in a turbulent flow, which establishes a quantitative relationship between friction stresses on the heat exchange surface and heat transfer through this surface. The article presents a method for determining the speed of the developed measuring system. An example of a successful application of the proposed method in relation to the study of thermomechanical processes in the gas exchange systems of reciprocating internal combustion engines is described.

Spectral analysis of gas dynamic processes in the inlet system of a piston engine with turbocharger

THE PURPOSE. To carry out a comparative analysis of the spectra of gas-dynamic characteristics of flows in the intake systems of piston engines with and without turbocharging, to assess the degree of influence of the turbocharger on the flow structure in such systems, and also to propose a method for the gas-dynamic improvement of processes in the system under consideration. METHODS. Due to the complexity of the object of research, an experimental approach was taken as a basis. The experiments were carried out on a single-cylinder piston engine model, which could be equipped with a turbocharger. A system for collecting and processing experimental data based on an analog-to-digital converter was used in the study. Data on changes in local values of velocity and static pressure of pulsating flows in the intake system during the engine's operating cycle were obtained using a constant temperature hot-wire anemometer and a fast-acting pressure sensor. Spectral analysis of functions of flow velocity and pressure versus time was carried out on the basis of the fast Fourier transform algorithm.RESULTS. The article presents a comparative analysis of the spectra of the amplitudes of the velocity and pressure pulsations in the intake system of an engine with and without turbocharging. Also proposed is a method for stabilizing the pulsating flow in the intake system by installing a leveling grid in the outlet channel of the turbocharger compressor. CONCLUSION. It is shown that the installation of a turbocharger leads to a significant change in the structure of gas flows in the intake system of the engine. It has been established that the presence of a leveling grid in the intake system of a turbocharged piston engine leads to a decrease in the low-frequency amplitudes of the flow velocity and pressure pulsations up to 30%. It is shown that the probability of failure-free operation of an automobile engine (cylinder diameter – 82 mm, piston stroke – 71 mm) increases by almost 1% when a leveling grille is used in the intake system.

Thermal-mechanical characteristics of stationary and pulsating gas-flows in a gas-dynamic system: In relation the exhaust system of an engine

It is a relevant objective in thermal physics and in building reciprocating internal combustion engines (RICE) to obtain new information about the thermal-mechanical characteristics of both stationary and pulsating gas-flows in a complex gas-dynamic system. The article discusses the physical features of the gas dynamics and heat transfer of flows along the length of a gas-dynamic system typical for RICE exhaust systems. Both an experimental set-up and experimental techniques are described. An indirect method for determining the local heat transfer coefficient of gas-flows in pipe-lines with a constant temperature hot-wire anemometer is proposed. The regularities of changes in the instantaneous values of the flow rate and the local heat transfer coefficient in time for stationary and pulsating gas-flows in different elements of the gas-dynamic system are obtained. The regularities of the change in the turbulence number of stationary and pulsating gas-flows along the length of reciprocating internal combustion engines gas-dynamic systems are established (it is shown that the turbulence number for a pulsating gas-flow is 1.3-2.1 times higher than for a stationary flow). The regularities of changes in the heat transfer coefficient along the length of the engine?s gas-dynamic system for stationary and pulsating gas-flows were identified (it was established that the heat transfer coefficient for a stationary flow is 1.05-1.4 times higher than for a pulsating flow). Empirical equations are obtained to determine the turbulence number and heat transfer coefficient along the length of the gas-dynamic system.

An experimental and numerical study of wind effects on a ground-mounted solar panel at different panel tilt angles and wind directions

The wind effects on a ground-mounted solar panel under the influence of the panel tilt angles and wind directions were investigated; both experimentally and numerically. The ground-mounted solar panel was used with tilt angles of 25° and 45° for a Reynolds number of 6.4 ​× ​104. Wind directions were varied from 0° to 180° at 30° intervals. A constant-temperature hot wire anemometer and a pressure scanner system were used to measure velocity and turbulence intensities and static pressure, respectively, in the wind tunnel. Numerical analyses were carried out via computational fluid dynamics methodology using the realizable k-ε turbulence model. The results showed that the flow structure had been significantly affected by the wind directions and panel tilt angles. The higher panel tilt angle caused stronger vortex shedding fluctuations, and higher velocity zones shedding frequencies. As with the flow structure, the design-relevant wind loads on the solar panel were also shown to be dependent on the wind direction and panel angle. The net pressure coefficients of the solar panel increased with the higher panel tilt angle. The critical wind directions were obtained as 300 and 1500 in terms of overturning moments, while 1800 and 00 wind directions were critical in terms of uplift and drag, respectively. The numerical results of the wind loads showed a good agreement with the experimental results.

Experimental investigation of the effects of length-to-diameter ratio of hot-wire sensor on the dynamic response to velocity fluctuations

This paper reconsidered the criterion on the length-to-diameter ratio (l/d) of the hot-wire sensor, $$l/d \ge 200$$ , for end-conduction effects on the dynamic response of constant-temperature hot-wire anemometer (CTA) to be neglected. Experiments were first conducted using a low-noise compact CTA with hot-wire sensors of l/d = 80, 120, 150 and 200 in a two-dimensional (2-D) circular cylinder wake at a Reynolds number Re = 77, at which a 2-D von Karman vortex street developed, allowing us to exclude spatial filtering and tangential velocity effects. The damping coefficient in the CTA bridge was tuned to 0.70 for all sensors to reduce possible influences of over- or under-damping on measurements in a frequency range up to 6 kHz. The stubs and prongs of probes consisted of identical materials and dimensions so that the thermal properties were considered to be identical for all probes. Careful comparisons of the amplitudes of the fundamental (1.9 kHz) and higher harmonic components of time-periodic wake vortices showed that the attenuation due to the end-conduction effect in the absence of the spatial filtering and damping coefficient effects was at most 2.5% in terms of the rms value of velocity fluctuations even for l/d = 80. The similar weak attenuation (about 2.6% for l/d = 80) was also observed in the measurements of low-frequency free-stream turbulence. In addition, effects of l/d on the yaw angle response of the sensor were examined in the free stream, revealing that the yaw angle ( $$\psi $$ ) variation of the measured velocity (both the mean and fluctuations) obeyed the cosine law for $$\psi \le 60^\circ $$ . The Champagne constant k was 0.12 for l/d = 200 and 0.2 even for l/d = 80 in the mean velocity measurement using the present probe with long stubs. On the other hand, the intensity of free stream turbulence measured using a $$45^\circ $$ -yawed sensor was significantly affected by the sensor’s l/d; the rms value of velocity fluctuation was attenuated by about 7.5% for l/d = 80.

Experimental research into the methods for controlling the thermal-mechanical characteristics of pulsating gas flows in the intake system of a turbocharged engine model

It is a relevant objective in thermal physics and piston engine construction to develop technical solutions for controlling the gas dynamics and heat exchange of gas flows in the intake system of turbocharged engines in order to improve performance. The article presents other authors’ data on the improvement of processes in the gas exchange systems of piston engines. It also provides a description of experimental set-ups, instruments, measurement tools and research methods for establishing the thermal-mechanical characteristics of pulsating flows in the intake system of a turbocharged engine. The instantaneous values of the gas flow rate and the local heat transfer coefficient were determined using the measured results by applying a constant temperature hot-wire anemometer (H-WA). The article describes technical solutions for influencing the gas dynamics and heat exchange of gas flows by stabilising and turbulising the flow. The regularities of changes in the instantaneous values of the flow velocity, pressure and the local heat transfer coefficient in time for a pulsating gas flow with different intake system configurations are obtained. It is shown that the installation of a levelling grid in the compressor outlet channel leads to the stabilisation of the flow and the suppression of heat transfer in the engine intake system by an average of 15% compared to the base system. It was found that the presence of a channel with grooves in the intake system leads to flow turbulisation and the intensification of heat transfer in the intake system by an average of 25%.

Separation Control and Heat Transfer over a Fence inside an Asymmetric Diffuser (Dept.M)

The present work is concerned with an experimental investigation of flow and Heat transfer through a fence located in an asymmetric plane two-dimensional diffuser. The average velocity and fluctuation fields have been measured with a constant temperature hot-wire anemometer (CTA). However, pressures in reversed flow regions have been measured using 5-hole-probe. Of special interest is the influence of the fence on measuring the velocity and the pressure of the flow in relation with heal faster parameters at five well-chosen stations of the diffuser. The obtained experimental data are used to provide a comparison between the cases of using and not using the fence for the sake of separation control and Consequently the determination of the variation of Stanton and Nusselt numbers, particularly in the separated regions. Also, the investigation is reported for some attributes about the sensitivity of the separated and reversed flow regions, that represent a range of flows in which the controlling mechanisms are largely unknown

Heat transfer from a single and row of three dimensional wall jets - A combined experimental and numerical study

This paper reports the results of experimental and numerical studies to understand the heat transfer characteristics of three-dimensional wall jets exiting from a single and a row of circular jet openings over an unheated flat plate. Infrared thermography is employed to obtain the temperature distribution over the target surface, and the semi-infinite approximation methodology is used to estimate the heat transfer coefficients. Single wire constant temperature hot-wire anemometer is used to measure the flow characteristics. Additionally, computational studies have been performed to select a suitable low Reynolds number turbulence closure models among the following models, namely (i) Spalart Almaras (SA) (ii) Realizable k-ε with enhanced wall treatment (RKE-ewt) (iii) k-ω SST and (iv) Reynolds Stress Model with enhanced wall treatment (RSM-ewt) that predicts the experimentally obtained results for heat transfer characteristics accurately. Based on the investigations carried out, it is observed that RKE-ewt turbulence closure model is not only accurate but also faster in the prediction of heat transfer coefficient. Further, it is also seen that for a fixed mass flow rate, and at a given diameter of the jet opening, widely spaced jets show higher heat transfer coefficients. Furthermore, for a row of three-dimensional wall jets correlations based on the numerical results are developed for the Nusselt number for a Reynolds number range of 5000 to 15000.

Experimental Investigation on Velocity and Temperature Field in a Rotating Non-isothermal Turbulent Boundary Layer using Hot-wire

This experiment measured the instantaneous temperature and velocity field synchronously in non-isothermal turbulent boundary layer in a rotating straight channel with a parallel-array hot-wire probe. The Reynolds number based on the bulk mean velocity (U) and hydraulic diameter (D) is 19000, and the rotation numbers are 0, 0.07, 0.14, 0.21 and 0.28. The mean velocity u and mean temperature T as well as their fluctuating quantity u’ and T’ were measured at three streamwise locations (x/D = 4.06, 5.31, 6.56). A method for temperature-changing calibration with constant temperature hot-wire anemometers was proposed. It achieved the calibration in operational temperature range (15.5 °C–50 °C) of the hot-wire via a home-made heating section. The measurement system can obtain the velocity and temperature in a non-isothermal turbulent boundary layer at rotating conditions. The result analysis mainly contains the dimensionless mean temperature, temperature fluctuation as well as its skewness and flatness and streamwise turbulent heat flux. For the trailing side, the rotation effect is more obvious, and makes the dimensionless temperature profiles lower than that under static conditions. The dimensionless streamwise heat flux shows a linear decrease trend in the boundary layer. It is hoped that this research can improve our understanding of the flow and heat transfer mechanism in the internal cooling passages of turbine rotor blades.