Time-resolved particle image velocimetry is implemented with a camera array and several laser sheets; this results in a multi-spatio-temporal scale system that is modular and flexible. The setup is optimized to capture global flow features, while locally resolving in space and time near the Kolmogorov scale. The apparatus relies extensively on machine vision CMOS cameras; they are inexpensive and stream

High-spatial-resolution (HSR) two-component, two-dimensional particle-image-velocimetry (2C-2D PIV) measurements of a zero-pressure-gradient (ZPG) turbulent boundary layer (TBL) and an adverse-pressure-gradient (APG)-TBL were taken in the Laboratoire de Mécan–ique des Fluides de Lille (LMFL) High Reynolds number Boundary Layer Wind Tunnel. The ZPG-TBL has a momentum-thickness based Reynolds number

The influence of buoyancy on pressure oscillation amplitude and frequency was studied with two steam jet directions in the range of steam mass flux 8.34-50.13 kg/(m2·s) and water temperature 40-85℃. At small steam mass flux, the steam bubble pattern of vertical downward jet is attached bubble regime because the direction of steam momentum and buoyancy are opposite. The pressure oscillation frequency

In this study, temperature field estimation was performed via time-of-arrival measurements of acoustic waves and using machine learning. An axisymmetric combustion field created by a McKenna burner was chosen as the measurement region. Electrical discharges served as the acoustic point source, and the acoustic travel times were measured using microphones installed along the periphery of the measurement

The flow patterns and the plug hydrodynamics of liquid-liquid two-phase flow in a small circular channel were experimentally investigated. Five distinct flow patterns, including droplet flow, slug flow, throat-annular flow, annular flow and stratified flow were observed in the silicone oil-water system. The flow pattern map was present systematically based on Re, We, water volume fraction and mixture

In this study, spark assisted compression ignition (SACI) combustion was investigated using PRF95 (a low reactivity high octane reference fuel of common commercial gasoline), a mixture of 95% isooctane (by volume) and 5% n-heptane (by volume) with a RON of 95 and compared with pure compression-ignition without spark. Characteristics like the cumulative heat release (CHR) and the heat release rates

Lean combustion can greatly improve the thermal efficiency of gasoline engine. Increasing ignition energy and tumble level can effectively expand its application range. Optical glass liner was used to clearly observe the in-cylinder state. Particle image velocimetry(PIV) was used for quantitative evaluation of tumble modification. The integral tumble ratio of the high tumble intake port is 1.67 times

Understanding condensation of CO2 is essential for e.g designing compact heat exchangers or processes involved in Carbon Capture and Storage. However, a consistent experimental campaign for condensation of CO2 on common materials is lacking. In this work, we present an experimental method and an associated laboratory setup for measuring the heat transfer properties of CO2 condensation on materials

As one fundamental flow structure, the vortex ring behind an impulsively starting disc can vividly characterize the vortex structure around the flapping flight and the drag-based paddling propulsions. In this paper, an elaborate experiment is performed to investigate the formation of the vortex rings (termed as DVR) by using digital particle image velocimetry (DPIV), as well as by investigating the

Experiments were conducted to measure condensation heat transfer of steam-ethanol mixtures on a horizontal smooth tube. Heat flux and vapor-to-surface temperature difference were accurately measured over a wide range of mass concentration of ethanol (0.001%, 0.005%, 0.01%, 0.025%, 0.05%, 0.1%, 0.5% and 1.0%.) at atmospheric pressure. The present work extends earlier data of Murase et al. (2007) and

The aim of this study was to investigate the effects of installing the grooved and smooth control cylinder upstream of a circular bare cylinder with a focus on the heat transfer and the flow structure behind the bare cylinder. The Reynolds number based on the bare cylinder diameter (D = 50 mm) is Re = 5 000. Control cylinder has a constant diameter as d = 25 mm. Flow characteristics and heat transfer

The initial spreading phenomena of oil droplets on a partially wettable surface under various surrounding pressures was conducted through an experimental investigation outlined in this study. The gauge pressure of the surrounding medium was varied stepwise in the range from atmospheric pressure to 30 MPa. Upon contact with the surface, spreading alters the total energy of the system. The timescale

A spherical particle with a diameter of 25.4 mm and density of 2640 kg/m3 was launched vertically upward toward the free surface of calm water. The Froude number of the particle passing through the water surface was varied. The dependence of the Froude number on the particle motion and water surface behavior was investigated from the instant the particle crossed the water surface until it attained

To clear the effects of the hydrodynamic interactions among neighboring vapor bubbles on the saturated pool boiling heat transfer, artificial nucleation sites with several cavity arrangements were manufactured on the substrate surface and measured liquid temperatures near heated substrate by a miniature thermocouple probe with 10 kHz. The surface temperature of heated substrate was measured by an infrared

This paper presents an experimental study to explore the feasibility of utilizing a swirling inverse diffusion flame (IDF) jet for impingement heating. The investigation concentrates on the impinging flame structure and impingement heat transfer. The effects of air swirling, the air jet Reynolds number, Rea, the global equivalence ratio, Φ, and the non-dimensional burner-to-plate distance, H/da, on

This study experimentally investigates the axial heat transfer of the secondary flow in the cylindrical annular gap around a flywheel within a canned reactor coolant pump, belonging to the Taylor-Couette (TC) flow. A dynamic method based on the transient temperature responses of the TC flow to the input thermal waves, where the axial heat transfer coefficient is determined by the amplitude decay and

Motivated by the importance of spray evaluation of viscous bioliquids prior to their deployments in combustion devices for heat and power generation, an aqueous surrogate was developed using water, glycerol, and a surfactant for nozzle design and optimization purposes. It provides a safe, clean, and transparent alternative for the spray characterization of bioliquids in a laboratory environment, compatible

Variations in fluid temperature are the most important error source in hot-wire anemometer measurements and must sometimes be compensated for. Although many temperature compensation schemes have been proposed over the years, no consensus seems to be reached regarding correction methods. In this paper new precision measurements on heat transfer from heated wires have confirmed that, provided the fluid

The turbulent strain rate generated by a pair of 25.4 mm tall and 12.7 mm wide (W) rectangular strips at a Reynolds number based on the strip width of 8500 was measured using a 3D hotwire probe in a wind tunnel. The strips were placed side-by-side separated by 3 W, 2 W, and 1 W. The convective heat transfer enhancement, denoted by the normalized Nusselt number (Nu/Nu0), was correlated with turbulence

A robust and easy-to-apply automatic static mask generation technique for PIV images is described. The technique is used after background removal operations and requires an image ensemble with sufficient number of single-frame or double-frame PIV images. The technique does not require any prior knowledge of the flow, illumination conditions, the bounding surface, or static object geometry. The technique

The present work is aimed at analyzing changes in the interfacial temperature distribution and interfacial heat flux distribution during sessile droplet evaporation. In particular, two kinds of nonintrusive measurement techniques, temperature-sensitive paint (TSP) and infrared imaging were used simultaneously. TSP was used to capture the interfacial temperature distribution, and then a one-dimensional

CHF is the maximal limit of heat flux in boiling heat transfer, therefore, it is a crucial parameter that has a fundamental impact on the security and economy of the nuclear system. An experimental investigation was carried out in the present study to identify the dominant CHF mechanism in a narrow rectangular channel at different gap sizes (2 mm and 3 mm). The visualization experiments were performed

Mechanisms for controlling the shock wave boundary layer interaction (SWBLI) by a plasma actuator array are investigated by two experiments. Low-frequency and high-frequency actuation modes are compared. The experimental results yield valuable insights into the control mechanism of SWBLI using a surface arc plasma actuator array. The schlieren snapshots and the mean and root mean square error of the

This experimental investigation discusses the effectiveness of shortfin mako shark skin to passively control turbulent boundary layer separation. Experiments were conducted in a water tunnel facility with the shark skin specimens mounted on a smooth flat plate subjected to an adverse pressure gradient. The two skin specimens have shark scales with different sizes, shapes, and bristling angles. The

The local phase distribution of adiabatic air-water two-phase flow in churn-turbulent to annular flows was experimentally investigated using the Two-Sensor Droplet-Capable Conductivity Probe. The experiments were performed in a 2.54 cm inner diameter vertical round pipe at downward flows. Twelve flow conditions in churn-turbulent to annular flows were chosen for the current study. The inlet superficial

The maldistribution in the parallel multiple channels commonly leads to a reduction in the efficiency of heat exchangers and even causes the equipment to suffer the risk of failure. The distribution of gas–liquid two-phase slug flow when moving through the parallel multiple channels is still an unresolved problem and limited by the lack of experimental data. This work presents an experimental study

The magnitude of surface heat flux and its accurate estimation are very crucial owing to their applicability in impulsive thermal loads for high-speed flights. The correctness of such heat flux is associated with the implications from highly responsive thermal sensors in ground-based aerodynamic studies. In the present study, the performance effectiveness of an indigenous, in-house-made coaxial thermal

Condensation of steam at a low mass flux inside an inclined tube was experimentally investigated to aid the optimal design of air-cooled passive heat exchangers for advanced LWRs. While varying downward inclination angle from 0 to 90°, the heat transfer coefficient monotonically improved by more than 15% while previous studies that have used refrigerants have reported that the optimal angle is between

Abstract The formation and evolution of volumetric flow structures from a rectangular orifice synthetic jet ( AR = 10 , Re = 550 , Sr = 0.0117 , and L o = 0.0855 m ) impinging on a flat plate is investigated using phase-locked single-camera light-field particle image velocimetry (LF-PIV). An impinging plate is located 24 orifice widths away from the rectangle orifice and this volumetric flow data is

Abstract Flow dynamics of a two-dimensional liquid sheet injected transversely into a subsonic airstream was comprehensively investigated. An injector with an aspect ratio of 90 and a thickness of 0.35 mm was used to produce the two-dimensional liquid flow. Experimental visualizations were used to identify the main features of the liquid sheet in crossflow. Tests were conducted for a wide range of

Abstract We report a systematic experimental study to characterise the isothermal flow-field within a vortex-based solar cavity receiver with an open aperture. Measurements were performed using particle image velocimetry for a fixed flow rate through the inlet jets to achieve Reynolds number of ReD = 11800. A range of flowrates through the outlet were assessed for a fixed inlet flow rate, including

Abstract We experimentally explored the distinct effects induced by the geometry of various axisymmetric orifices in the near and intermediate regions of jets at a Reynolds number of Re ≈ 10 5 based on the diameter, d = 10 mm, of the orifices. The orifices inspected had thicknesses of ∊ / d = 0.2 , 1 and 2 and divergence angles of θ = 0 ∘ , 20 ∘ and 45 ∘ . High-speed planar particle image velocimetry

Abstract An experimental study of a simple NACA 0012 airfoil fitted with two different flap profiles was carried out to characterize their aerodynamic and aeroacoustic performance. The airfoil with a flap deflection angle of β = 10 ° was tested for a wide range of angles of attack at a chord-based Reynolds number of Re c = 2.6 × 10 5 . The aerodynamic lift and drag measurements show improved lift-to-drag

The denoising of Lagrangian trajectories based on regularized B-spline is investigated. The aim is to find systematic criteria for optimization of algorithms used in 4D-PTV in order to optimize the quality of 4D-PTV measurements of turbulent flows as well as high-order of turbulence statistics. We introduce and adapt to this context two innovative tuning strategies which are commonly used in the Tikhonov

Natural convection heat transfer from three isothermally heated horizontal cylinders submerged in water in a triangular arrangement is investigated. Two configurations, named here as one over two and two over one, are characterised for three cylinder spacings (S = 2, 3 and 4 cylinder diameters) and Rayleigh number conditions (Ra = 2×106, 4 × 106 and 6 × 106). Combined local heat flux measurements and

The current work presents a study of qualitative relationships between the flow unsteadiness, induced by nozzle geometry variation, and non-equilibrium condensation behavior at high temporal scales for supercritical carbon dioxide (sCO2) flow. A closed sCO2 loop facility is used to drive a supercritical carbon dioxide flow through a rectangular converging–diverging channel. As the flow traverses through

The combustion of an oxygen/paraffin hybrid rocket motor was experimentally characterized. Firing tests were conducted for different oxidizer mass fluxes ranging from 2.47 to 3.40 g/ (cm2·s). Variations in temperature and H2O partial pressure at the nozzle exit were diagnosed using mid-infrared tunable diode laser absorption spectroscopy (TDLAS) based on H2O absorption near 2.5 μm. Three H2O absorption

Coupling structures of buoyancy induced thermal convection in two immiscible layers with and without weak background rotation were investigated in laboratory experiments using a glycerol solution and a silicon oil as the test fluids. A cylindrical vessel was employed to yield three-dimensional (3D) development of the two-layer convection, and the influence of background rotation on convective motion

In this study, the placement of a micro-vortex generator (VG) upstream of the film cooling hole is proposed to improve the film cooling performance. The film cooling effectiveness and flow characteristics at three blowing ratios (M = 0.2, 0.4, and 0.8) are measured by using pressure-sensitive paint (PSP) and particle image velocimetry (PIV), respectively. The results indicate that the VG upstream of

Two-phase pressure drop is studied in a transparent cross-corrugated channel for uniform and non-uniform gas–liquid distribution. Both uniform and non-uniform distribution are created by injecting air and water through different numbers of nozzles directly into the channel. The frictional pressure drop clearly indicates the impact of maldistribution. The single channel is pivot-mounted to allow horizontal

Hydraulic jumps occur commonly in natural channels and energy dissipation systems of hydraulic structures in the violent transition from supercritical to subcritical flows. They are characterised by large flow aeration, high turbulence and strong fluctuations of the free surface and the jump toe. For free surface measurements, fast-sampling, fixed-point instruments such as acoustic displacement meters

Multiple orifice synthetic jet devices are becoming widely utilized for active flow control and jet impingement cooling, due to its mixing performance resulting from the vortices and jet interaction. Therefore, understanding the flow interaction between multiple synthetic jets is crucial in maximizing the potential for many industrial applications. In the present study, an experimental investigation

The boundary layer detachment limits compact power plants' operation at moderate Reynolds number in adverse pressure conditions. Flow detachment is promoted by the lack of momentum in the near-wall region when exposed to adverse pressure gradients. Transient flows or periodic flow perturbations may delay or prevent the flow detachment. The present investigation experimentally analyzes the behavior

Experiments were conducted to explore the droplet generation process when an ascending liquid spray impacts on a downward-facing solid surface. The droplets generated in the present experiments were classified into the two types: one is the splashing droplets generated by the impacts of droplets in spray and the other is the falling droplets produced from a liquid film formed on the solid surface.

Abstract Acoustic measurements and time-resolved schlieren visualizations are performed on underexpanded jets issuing from a convergent nozzle to investigate the screech feedback loop and the mode staging phenomenon. In the present experiments, the nozzle pressure ratio ranges from 2.00 to 4.00. The instability mode of the jet successively experiences the axisymmetric A1 and A2 modes, the flapping

Abstract Bubble behavior in a hydrogen evolving system was compared to that under boiling conditions. Hydrogen was generated electrochemically in an aqueous solution of 1.5 M sulfuric acid (H2SO4). Hydrogen bubble parameters such as active nucleation site density, bubble departure diameter, and bubble frequency, were measured and compared to those observed during boiling. The hydrogen evolving system

Abstract Boundary layer thickness measurements have been taken via spectroscopic methods in the past, but were traditionally limited to a single point of view due to the need of an excitation source (such as a laser) and a detector. A new optical technique that measures the broadband filtered natural emissions of species does not require an excitation source to measure the boundary layer and thus can

Abstract The impaction-pin spray nozzle is widely used in chemical and process industries. To study the atomization characteristics of the impaction-pin nozzle, a high-pressure atomization apparatus was developed and an optical imaging system for the measurement of droplet parameters was proposed. The droplet size and velocity vector were extracted from the shadowgraph images and the influence of liquid

Self-excited noise generation from laminar flames in thin annular jets of methane/air premixture has been investigated experimentally. Various flames were observed in this flow configuration, including conical shape flames, ring shape flames, steady crown shape flames, and Oscillating crown shape flames. Self-excited noise with the total sound pressure level of about 70dB was generated from the oscillating

Abstract This paper presents a method for fast estimation of the enthalpy-temperature function of Phase Change Materials (PCMs). The method combines a simple experimental setup with a non-iterative, reliable mathematical algorithm that allows retrieving the enthalpy-temperature function from measurements of heat flux and temperature at a single point. Distilled water was used as reference PCM for validation

Abstract A combination of the Linear Stochastic Estimation (LSE) and a modified version of the Extended Proper Orthogonal Decomposition (EPOD) is proposed to link multi-plane particle image velocimetry (PIV) data describing transitional separated boundary layers. Measurements have been obtained in two orthogonal planes, which share a common line providing the spatial consistency between the data sets

Abstract This work presents the design and the validation of a non-intrusive capacitance - based densimeter, for the on-line measurement of solid fraction in a slurry pipe flow. An asymmetrical type capacitance sensor was designed by means of numerical electric field analysis. The simulations conducted at different solid volume fractions revealed that the sensor is not sensitive to the distribution

Abstract Heat transfer deterioration in turbulent mixed convection affects the performance and safety of various pieces of industrial equipment. The reactor cavity cooling system (RCCS), a passive safety system in a very high temperature gas-cooled nuclear reactor (VHTR), incorporates rectangular riser channels to remove residual heat emitted from the reactor vessel, where turbulent mixed convection

Abstract This work aims to control the unsteady flow structure of a NACA0012 under full stall by limiting the vortex roll-up from its trailing edge. In this regard, plates with varying lengths at zero incidences were attached at the trailing edge of the airfoil at an angle of attack of α = 16o and low Reynolds number of Rec = 2.0×104. Under these conditions, the flow separates near the leading edge

Mars and upper Earth atmosphere missions are booming in recent years increasing the interest in heat transfer in rarefied gases. At these low pressures, the heat transfer problems involving small geometries whose characteristic length is of the order of the mean free path of the gas molecules, raises new difficulties. This being especially severe in the case of free convection, where the velocity of

Abstract An experimental study on the compact lean premixed flames stabilized on a bluff-body and swirl burner is performed. The flames are featured with a strengthened Inner Recirculation Zone (IRZ). The objective is to identify the critical causes of blow-off near the lean limit. Meanwhile, the effects of hydrogen addition on the flame stabilization are also examined. Premixed CH4/H2/air mixtures

Fuel concentration information is critical to the development of high-efficiency combustion system of direct-injection natural gas engines. In this study, a one-dimensional (1-D) measurement approach based on laser induced breakdown spectroscopy (LIBS) is developed to quantitatively measure 1-D fuel concentration distributions in gas jets at high ambient pressures. Except for the spectral dimension