Sharp-edged Orifice Research Articles

Analysis of upper and lower nappe profiles of large orifice for the design of bottom and roof profiles of high head orifice spillway

Abstract Large orifices are constructed for dams to release water and sediments from reservoirs. Such structures are called submerged spillways. Numerous studies have investigated discharge coefficient, velocity coefficient, and head loss coefficient of large orifices; however, the literature lacks data on the upper and lower nappes of the jets from these orifices. In the present experimental study, the upper and lower nappes are investigated up to 80 m head at different gate openings. The observed minor deviation between the lower nappe profile and trajectory profile equation suggests sensitivity to different factors. The significant role of the coefficient of velocity, averaging at 0.926, highlights its impact on minor deviation. Subsequently, the impact of the solid bottom profile on the discharge coefficient and upper nappe profile are also examined. The results show improvement in discharge coefficient of a sharp-edged large orifice, which increased from 0.69 to 0.74. The results also indicate that the upper nappe profiles and United States Bureau of Reclamation (USBR) profiles are similar. The improvement in the upper nappe profile indicates the significant role of the solid bottom profile, which consequently was found to be helpful in defining the roof profile of an orifice spillway. .

Effect of Dissolved Carbon Dioxide on Cavitation in a Circular Orifice

In this work, we investigate the effect of dissolved gas concentration on cavitation inception and cavitation development in a transparent sharp-edged orifice, similar to that previously analyzed by Nurick in the context of liquid injectors. The working liquid is water, and carbon dioxide is employed as a non-condensable dissolved gas. Cavitation inception points are determined for different dissolved gas concentration levels by measuring wall-static pressures just downstream of the orifice contraction and visually observing the onset of a localized (vapor) bubble cloud formation and collapse. Cavitation onset correlates with a plateau in wall-static pressure measurements as a function of a cavitation number. An increase in the amount of dissolved carbon dioxide is found to increase the cavitation number at which the onset of cavitation occurs. The transition from cloud cavitation to extended-sheet or full cavitation along the entire orifice length occurs suddenly and is shifted to higher cavitation numbers with increasing dissolved gas content. Volume flow rate measurements are performed to determine the change in the discharge coefficient with the cavitation number and dissolved gas content for the investigated cases. CFD analyses are carried out based on the cavitation model by Zwart et al. and the model by Yang et al. to account for non-condensable gases. Discharge coefficients obtained from the numerical simulations are in good agreement with experimental values, although they are slightly higher in the cavitating case. The earlier onset of fluid cavitation (i.e., cavitation inception at higher cavitation numbers) with increasing dissolved carbon dioxide content is not predicted using the employed numerical model.

Heat Transfer and Pressure Loss Correlations for Leading Edge, Jet Impingement Using Racetrack-Shaped Jets With Filleted Edges

Abstract This paper presents an experimental investigation of heat transfer and pressure loss for leading-edge jet impingement using racetrack-shaped jets. The majority of literature for gas turbine cooling applications considers jet impingement using square or sharp-edged orifices. However, the edge of the jet orifices generally has some degree of filleting (or rounding) along the edges, due to casting the airfoils or material wear due to long-term operation. Engineers need data under realistic engine configurations to improve the utilization of coolant while adequately protecting the airfoil. The current experimental study is a parametric investigation of heat transfer and pressure loss for leading-edge jet impingement, where the effects of jet Reynolds number (Re = 10,000–100,000), jet–to–jet spacing (s/d = 2–8), jet–to–target surface spacing (z/d = 2–4), surface curvature (D/d = 2.67–5.33), and jet fillet–to–jet plate thickness (r/l = 0.16–0.5) are each considered. The edge rounding at both the inlet and outlet of the jet plate yields reduced heat transfer compared to the square-edged jets. However, the fillets significantly improve the discharge coefficients associated with the racetrack-shaped orifices. With the extensive testing completed in this study, design correlations have been developed to predict the surface Nusselt number and discharge coefficients, with 10% and 19% deviation from experimental results, respectively. Engine designers can predict the level of heat transfer and pressure loss for leading-edge jet impingement using these correlations.

A comparative study of circular and rectangular bended plunging jets

In the present work we study the topology, mixing properties, turbulence quantities, dependence on the outlet geometry of a sharp-edged orifice plunging jet which first issues horizontally in air and then plunges in a water pool. The investigated orifices shapes are circular and rectangular. Data are acquired at different Reynolds numbers in the range 11000–25000, based on the orifice diameter (equal to 2 cm) and on the average exit velocity, as derived from flow rate measurements. Velocity fields in vertical and horizontal planes are measured using planar time-resolved Particle Image Velocimetry. Results show a clear asymmetry of the cross-velocity profiles both in circular and rectangular cases, with the latter that revealed a shape which is Reynolds number dependent. Axial velocity decays, potential core lengths and spreading rates highlight an opposite trend between the two jet geometries, thus suggesting a higher mixing for the lowest Reynolds number circular jet and the highest rectangular one. Plunging angle shows a dependency on Reynolds number. Moreover, it seems to play a role in the evolution of the upper and lower side of the jet due to the onset of a co-flow. Ambient mass entrainment points out the different interactions of the two plunging jets with the ambient flow: in circular case, it entrains fluid from the surroundings, from horizontal to vertical planes in streamwise direction, while in rectangular one it ejects flow from vertical to horizontal planes. Finally, Strouhal numbers are derived for main vortices frequencies along jet centerline, other than upper and lower sides.

A new cavitation model for simulating steady and unsteady cavitating flows

Cavitation is a widespread hydrodynamic phenomenon. Accurate prediction of cavitating flow is beneficial to the design and maintenance of the hydrodynamic machinery. A new cavitation model reducing the number of parameters needed to obtain satisfactory results is presented and validated. Based on the multiphase flow equation, the mass transfer due to cavitation is expressed as a source term in the gas-phase continuity equation. The mass transfer rate is derived from the assumption that the number of cavitation nuclei per unit volume in the mixture varies linearly with the vapor volume fraction during the evaporation stage. The mass transfer rate also incorporates the simplified Rayleigh–Plesset equation and the critical radius of cavitation nuclei. The new cavitation model considers the influence of non-condensable gas and the molar density of non-condensable gas is the only physical parameter that must be specified. The cavitating flow over a hydrofoil, cavitating flow in a sharp-edged orifice, and the unsteady cavitating flow in a venturi tube were predicted to verify the validity of the new cavitation model. The simulation results of the new model are in good agreement with the experimental results. The new cavitation model predicts cavitation regions and periodic unsteady cavitating flows.

Influence of orifice thickness and chamfer on broadband noise in a water circuit

An incompressible large-eddy simulation (LES) is used to predict broadband noise generation by an orifice in a water circuit. Flow conditions are chosen in order to avoid cavitation. The model’s results are compared to measured wall pressure fluctuations for three orifices: a thin sharp-square-edge orifice, a thick sharp-square-edge orifice and a thick narrower orifice with an upstream chamfer. Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulations (LES) fail to reproduce the steady-flow drag coefficient of the thick sharp-edge orifice and of the upstream-chamfered orifice. Large differences are found in the steady-flow drag coefficient of different samples of the thick orifice. An edge-tone like instability is observed in the near-field pressure fluctuations of one of the thick sharp-square-edge orifices, which does not appear in the other samples and is suppressed by the upstream chamfer. However, there are only minor differences in far-field radiated sound for these thick sharp-edged orifices. A plane-wave model with acoustic source from the LES predicts the power spectral density (PSD) of the acoustic pressures within a factor 3. At low Strouhal numbers (based on the orifice diameter and the cross-sectional averaged velocity in the orifice) the thin orifice behaves similarly to the thicker strongly chamfered orifices, with thin central cylindrical section. At higher Strouhal numbers the measured and predicted acoustic-pressure fluctuations due to these orifices are two orders of magnitude lower than those of thick orifices with sharp square edges. As orifices are used for the control of the flow distribution through complex water-cooling networks, the good results for thick chamfered narrow orifices call for a further study to find shapes that minimize the sound production at constant static pressure drop.

Mechanical energy loss and Rayleigh-Taylor instability in free discharge of vertical sharp-edged orifices

Orifice discharge is a classical hydrodynamic phenomenon. The experiments of liquid free jets through vertical sharp-edged orifices were conducted on the influences of orifice geometry and liquid depth. The flow mechanism indicates that the higher energy loss of thin-walled orifice is caused by the inspired air annulus inside orifice channel which will lead to the Rayleigh-Taylor instability. The theoretical derivation further demonstrated that the consecutive collisions between main stream and surface waves can cause significant energy dissipation. Besides, a kind of transition orifice was found for the first time: the increase of liquid depth can induce a sudden switch from the thick-walled orifice mechanism to the thin-walled one. The presentation in this work on the formation and development of coherent structures, the migration and bursting of vortexes, as well as the interaction between vortexes and free interface, is universal for revealing the essential features of multi-phase flow in form friction.

Experimental investigation of flow and thermal characteristics of synthetic jetissuing from sharp-edged orifices

ABSTRACT The present experimental study reports the flow and heat transfer characteristics of a synthetic jet issuing from a sharp-edged orifice (diverging-shaped orifice). The experiments are carried out for a varied range of opening angles of sharp-edged orifices (θ = 0°, 30°, 60°, 90°, and 120°), Reynolds number (Re = 3243–8143), different jet-to-surface spacings (z/d = 1–16), and for two different values of orifice thicknesses, t = 5 mm (t/d = 0.33) and 10 mm (t/d = 0.66). The hot-wire anemometry is used to study the flow characteristics of synthetic jet, while heat transfer characteristics are studied by using a thermal imaging technique. The time-averaged flow fields associated with sharp-edged orifices reveal that orifices with t = 5 mm and 10 mm exhibit saddle-backed and top-hat velocity profile shapes, respectively. The results show that for a square-edge orifice (θ = 0°), the heat transfer rate decreases with an increase in orifice plate thickness from 5 to 10 mm, while the opposite trend in heat transfer is observed with sharp-edged orifice. The heat transfer rate with a 10 mm thick sharp-edged orifice is higher than the 5 mm thick sharp-edged orifice for all the tested opening angles. Furthermore, the results also show that for sharp-edged orifices, the heat transfer rate increases with the increase in opening angle from θ = 0° to 60°, while it decreases with further increasing from θ = 60° to 120°. The maximum value of average Nusselt number (Nuavg) is obtained for θ = 60° for both the orifice thicknesses (t = 5 and 10 mm), and this effect is found to be more pronounced for t = 10 mm orifice. For sharp-edged orifice (θ = 60°), the maximum enhancement in Nuavg is found to be 12.66% and 23% higher for t = 5 mm and 10 mm, respectively, compared to the equivalent square-edged orifice (θ = 0°). The cause for variation in heat transfer rate with sharp-edged orifices is interpreted due to the effect of flow recirculation and mass flow rate. A correlation has been proposed for Nuavg as a function of different opening angles. The present finding is useful for the optimization of the synthetic jet geometrical parameters for the effective heat transfer rate.

A three-dimensional Generalized Finite Element Method for simultaneous propagation of multiple hydraulic fractures from a wellbore

In this article, a 3-D methodology for the simulation of hydraulic fracture propagation using the Generalized Finite Element Method (GFEM) is extended for the simultaneous propagation and interaction of multiple hydraulic fractures. A 3-D isotropic elastic material for the rock and Reynolds lubrication theory for the fluid flow in the fractures are assumed. The elastic solid governing equation is discretized in space with a quadratic GFEM and the equation for the flow in the fractures is discretized in space with a quadratic FEM. With the GFEM, the solid mesh does not need to fit the fracture and accuracy is improved around the fracture front with the use of singular enrichment functions. Discretization error is further controlled by employing mesh adaptivity around the fracture front. The injected fluid partitioning among fractures is computed by modeling the wellbore, where the flow is assumed to be governed by the Hagen–Poiseuille relation. The pressure losses between wellbore and hydraulic fractures are modeled with the sharp-edged orifice equation and with the use of 1-D connecting elements. A linear FEM is adopted for the spatial discretization of the equation governing the flow in the wellbore and the connection between wellbore and hydraulic fracture. A propagation criterion based on a regularization of Irwin’s criterion is adopted and a methodology to automatically estimate the time step that leads to the propagation of fractures based on linear interpolation/extrapolation is presented. Three verification problems are solved and compared with results from the literature. A problem with initial fractures not aligned with the in situ stresses is analyzed. Complex final fracture geometries are observed due to this misalignment.

Analysis and optimisation design on damping orifice of oleo-pneumatic landing gear

AbstractThis paper investigates the feasibility of improving the aircraft landing performance by design the damping orifice parameters of the landing gear using lattice Boltzmann method coupled with the response surface method. The LBM is utilised to simulate characteristics of the damping orifice after model validation. The numerical model of the landing gear using simulated damping force is validated by single landing gear drop test. Based on the numerical model and the response surface functions, the sensitivity analysis and the optimisation design are performed. The maximum error of mean velocity simulated using LBM with experimental data is 7.07% for sharp-edged orifices. Moreover, the numerical model predicts the landing responses adequately, the maximum error with drop test data is 2.51%. The max overloading of the aircraft decreases by 5.44% after optimisation, which proves that this method is feasible to design the damping orifice for good landing performance.

Effects of differential pressure measurement characteristics on high pressure-EGR estimation error in SI-engines

With proper control, exhaust gas recirculation (EGR) can be used for knock mitigation in SI engines, enabling fuel economy improvements through more optimal combustion phasing and lower fuel-enrichment at high loads. Due to significant pressure pulsations across the EGR valve, estimating the mass flow rates at transient and reversing flows across the valve can be challenging. Many systems utilize the pressure drop across a restriction in a flow path as an indication of mass flow. In automotive applications, the measurement of the pressure drop is accomplished by the use of a delta pressure sensor and the pressure drop mechanism could be a sharp edge orifice or other restrictions such as a valve opening. This technique works well for steady-state flow; however, if pressure fluctuations exist, especially at higher frequencies, this method of measuring mass flow can have large errors. The accuracy of EGR mass flow estimation based on a pressure differential (Δ P) measurement and the steady compressible flow orifice equation is investigated for various Δ P sensor frequencies and sampling rates on Ford 3.5L V6 GTDI and 2.3L I4 GTDI engines. This paper identifies the two major contributors of the error are the long length of the gauge lines and the close location of the downstream tap. The long length of the gauge line results in resonances at low frequency which affects the sensor performance. When the downstream tap is placed too close to the orifice, the accuracy of sensor reading is reduced. The proposed solution suggests keeping the gauge line as short as possible and the downstream tap at least two diameters away from the orifice and using a high-speed sensor. The result from engine testing shows a great improvement in the measurement accuracy by 43%. It is demonstrated that using a slow responding sensor with a low sample rate leads to erroneous mass flow calculation when significant pressure pulsations exist. A minimum of 1 kHz sample rate is needed to increase the accuracy of the EGR estimate within ±1%.

Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines

Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion.

Effect of conical angle on the hydraulic properties of orifice plate flows: A numerical approach

Orifice flowmeters are widely used in industry due to their simple design, ruggedness, and easy installation. However, high-pressure losses, measurement accuracy, and long pipe length requirements are still significant concerns. Typically, conical entry orifice plates at a 45-degree conical angle are recommended by orifice standards, especially for low Reynolds numbers instead of the sharp-edged orifice plates, which pose stability. The primary goal here is to develop the conical entry orifice plates further over a broader range of Reynolds numbers. In this case, a 45-degree conical angle may seem questionable since the optimization of conical angles has not been studied so far. To clarify that point and reach the new technical data about the conical entry orifice plates, orifice plates in different orifice diameter ratios (0.4, 0.5, 0.63) and beveled with different conical angles (15°, 30°, 45°) were tested numerically through water flow simulations inside a pipe with an inner diameter of 50.8 mm at different Reynolds numbers (5000,18,400, 91,100, 240,000).According to the analysis made, the 30-degree conical angle orifice plate was the best in reducing pressure losses, resulting in pressure losses 37–52% less than that of sharp-edged orifice plates in the min-max range. Furthermore, it reduced the pressure losses by 13–21 % more than that of the 45-degree conical angle. These last outcomes indicate that current orifice standards needs a modification into the recommended conical angles. Through these findings, pressure losses in multi-hole plate flow conditioners can be reduced considerably when the holes are beveled at the 30-degree conical angle.Also in the study, the axial characteristic lengths relevant to recirculation region, flow recovery and vena contracta were predicted approximately, along with the derived numerical correlations resulting with constants. Moreover, the effect of orifice plates exposed to an upstream distorted velocity profile on orifice flows was tested numerically. According to this evaluation, the lowest measurement errors were observed at the 30-degree conical angle orifice plate, about 30–70 % less than that of the sharp-edged orifice plate in the min-max range.

A General Outflow Theory Based on Momentum Balance

Abstract One of the oldest problems in the history of hydraulics is the outflow from a vessel through an orifice. In 1644, it was described by the Torricelli principle stating that the outflow velocity is the fall velocity from the filling level. From a theoretical point of view, the Torricelli principle is valid because it follows from Bernoulli's energy conservation principle. In this paper, the outflow problem will be described by Newton's momentum balance principle. Here, the Torricelli formula is obtained when the rounded orifice is treated as a contraction. For the sharp-edged orifice the bulk outflow velocity is the fall velocity from half the filling height. In this momentum balance theory, no artificial outflow coefficients are needed to distinguish between the cases of sharp-edged and rounded orifices.

Characterisation of low-Reynolds number flow through an orifice: CFD results vs. laboratory data

Abstract Pressurised pipe systems transport fluids daily over long distances and sediment deposits are responsible for narrowing the cross-sectional area of the pipe. This reduces the carrying capacity in gravity pipes and increases the energy consumption in rising mains. As partial blockages do not give rise to any external evidence, they are considered the most insidious fault occurring in pipe systems. Thus, the refinement of reliable techniques for detecting partial blockages at an early stage is of great interest to water utilities. This paper presents a computational fluid dynamics (CFD)-based analysis of the steady-state flow through a sharp-edged orifice which corresponds to the most straightforward partial blockage feature in a pipe. The main motivation is the fact that the interaction between pressure waves and a partial blockage – on which Transient Test-Based Techniques for fault detection are based – is strongly influenced by the pre-transient conditions at the partial blockage. The refined CFD model has been validated by considering experimental data selected from the literature. The comparison of obtained results demonstrates good performance of the numerical model. This authorised exploring in detail the features of the flow through the orifice as a necessary premise to its use within the successive transient analysis.

Supercritical Water Choking Flow Experiments Through a Convergent-Divergent Test Section

Abstract The heat transport system of Gen-IV supercritical water-cooled reactors (SCWRs) will operate at pressures close to 25 MPa and outlet temperatures of up to 625 °C. The design and safety analyses of this type of reactors still necessitate among others, experimental information and validation of critical (choked) flows models of water above the thermodynamic critical state. Up to now, choked flow data were collected at atmospheric discharge pressure conditions, without changing the discharge pressure to verify the occurrence of choking flow; in most of the cases, using fluids different from water. This paper presents experimental supercritical water choking flow data collected by using a convergent-divergent test section by changing the discharge pressure to verify the occurrence of choked flow. The critical mass flux is presented as a function of the temperature difference between a pseudo-critical temperature and the bulk fluid temperature. This representation allows us to assess similar experiments performed by using different test sections. Hence, a comparison of actual data with those previously obtained using 1.0 mm and 1.4 mm diameter sharp-edged orifices, shows peculiar differences. The actual experiments were limited by very low values of choking mass flow rates. Furthermore, in some cases, it was observed the presence of an increase in the discharge pressure that seems to indicate the existence of shock-wave structures. We are also able to estimate a pseudo-critical temperature difference below which choking flow systematically occurs.

An experimental study on the discharge coefficient of a sharped-edged hydraulic orifice

Aiming at performing basic research on fluid mechanics of hydraulic orifices under high or low temperature conditions, in this study, a novel compact experimental module, which integrates the oil, the oil supply mechanism, the test valve with orifice and several sensors, was firstly developed, the experimental module can be wholly placed into a high/low temperature chamber to undertake experiments; Based on the integrated experimental module, an automatic measurement test rig was further developed. By using the test rig, experiments on flow characteristics of a sharp-edged hydraulic orifice, which uses the anti-wear hydraulic oil HM46 as the working fluid, were conducted in a temperature range of -10°C∼+80°C, the Flow-Pressure Characteristics and Discharge Coefficient of the hydraulic orifice were obtained by curve fitting, the effects of different temperatures on the Discharge Coefficient and damping force were finally investigated. The results show that in the temperature range up to room temperature of 20°C, the Flow-Pressure characteristics, the Discharge Coefficient and damping force of the sharp-edged orifice are not sensitive to temperature changes, but when the temperature is below room temperatures, the discharge coefficient drops linearly, and the damping force increases with the decreasing of temperatures.

Experiments on the flow characteristics of hydraulic orifices under high or low temperature conditions

A new test rig with a compact experimental module has been developed in this study to support experiments on fluid mechanics of hydraulic orifices under high or low temperature conditions, by using the test rig, experiments on flow characteristics of a sharp-edged orifice and a thick-wall orifice were conducted in a temperature range of -10°C∼+80°C. Experimental results show that in a wide temperature range, the Flow-Pressure characteristics of the sharp-edged orifice are not sensitive to temperature changes, but that of the thick-wall orifice will vary obviously at different temperatures; In the temperature range up to 20°C, the Discharge coefficients and Damping forces of both of the two orifices remain at constants, however, when the fluid temperature is below 20°C, Discharge coefficients of the two orifice will drop linearly, damping forces of the two orifice will increase, but discharge coefficient and damping force of the thick-wall orifice will respectively drop and increase more sharply than that of the sharp-edged orifice, so this indicates that at low temperature conditions the fluid resistance and energy loss when it passes through a thick-wall orifice are larger than that when it passes through a sharp-edged orifice.

RANS 난류 모델을 이용한 직각 모서리형 오리피스 내부의 캐비테이션 유동 예측으로부터 얻은 교훈

In-service testing (IST) related system in the nuclear power plant has various types and sizes of orifices for flow control and decompression. Rapid flow acceleration and accompanying pressure drop may cause cavitation inside the orifice, which may result in orifice degradation and structural damage. Since cavitating flows involve complex turbulent two-phase flows, the accurate simulation of this flow by using the available computational fluid dynamics (CFD) software is still a great challenge. In this paper, to assess the prediction accuracy of different Reynolds-averaged Navier-Stokes (RANS)-based turbulence models for the analysis of cavitating flow inside a sharp-edged orifice, the simulation was conducted with the commercial CFD software, ANSYS CFX R18.1. The predicted results were then compared with the correlation based on measured data. Through this comparative study, it was concluded that turbulence models are one of the main factors providing the uncertainties in the simulation of the orifice cavitation flow and therefore, licensing applicants should carefully validate the appropriate selection of the turbulence models when they use the computational result for the orifice cavitation flow as the base data of a licensing document.

A phase averaged PIV study of circular and non-circular synthetic turbulent jets issuing from sharp edge orifices

An extensive experimental study using Particle Image Velocimetry (PIV) on synthetic jets issuing from different orifice shapes is reported. All data are phase and time averaged to derive mean velocity, half-velocity width and rms velocity profiles in the near field of the jet (0 < X/D < 7), at a Reynolds number around 10,000. Different non-circular orifice shapes as rectangular, square, elliptic and triangular are considered and results are compared to those of the circular orifice in order to investigate the effect of asymmetry on the turbulent flow field in view of mixing enhancement. The measurements are carried out on two orthogonal planes to capture three dimensional features of non-circular jets. Results show highest velocity decay rate for elongated orifices, especially the rectangular one, in comparison to the circular one, both in phase and time-averaged plots. Time averaged results show higher velocity decay rate of synthetic jets in comparison to those of continuous ones. It is also observed that, for X/D > 5, only profiles of circular and square jets become partially self-similar. For synthetic jets, higher turbulence content is measured for all orifice shapes at the centerline and close to the orifice exit in comparison to continuous jets.