Unsteady two-dimensional orifice flow: a large-size experimental investigation Ecoulement non-permanent dans un orifice rectangulaire: une étude experimentale de grande taille (original) (raw)
Related papers
2013
An unsteady experimental study was completed with the intention of identifying a transition region between partially full weir flow and fully developed orifice flow for a circular sharpedged orifice. Three orifices of different diameter were tested. The head-discharge relationships were obtained by pressure recordings and directly compared by using dimensional analysis. The presence of true weir and orifice flow behaviour was evaluated by an original technique where the head exponent in the head-discharge relationship is considered. The study found that true orifice behaviour was achieved in the experiments. Correspondingly, based on the head exponent, no evidence was obtained to support the existence of a different flow behaviour within the transition. Nevertheless, the experimental data have indicated that corrections are required to be applied to the discharge coefficient in the transition domain. A set of steady state experiments verified the unsteady data results in the orifice flow regime. Discharge coefficients were calculated and predicted by a fitted equation for a circular sharp-edged orifice across the entire range of head. Comparisons to the commonly used orifice equation validate its use for design.
Characteristics of flow through orifice-meter
JES. Journal of Engineering Sciences/JES. Journal of engineering sciences, 2024
Flow measurements in pipes and open channels are critical for successful water resource management as the economic value of water has increased. Orifice meters are typically used as flow-measuring devices in pipes because they are cheap and simple compared to other devices. Also, orifices are used as energy dissipation methods in water hammer protection devices and hydroelectric power tunnels. Although traditional circular orifice meters have been extensively studied, many points need to be studied. So, experimental and numerical research is carried out to study the effect of orifice geometry on energy loss and the discharge coefficient. The experimental tests are carried out using two different types of orifice plates: circular and triangular, for each one the cross-sectional area is changed four times. The orifice is installed on a 10 cm diameter transparent pipe. The flow rate is changed ten times for each orifice ranging from 13.8 to 49.2 m3/hr. A general correlation equation for the coefficient of discharge is deduced. It was found that the triangular orifice shapes are better than the circular orifice shapes in terms of performance, with reduced head loss and a larger discharge coefficient. By using computational fluid dynamics techniques, the flow behavior through the orifice is analyzed by ANSYS Fluent software. The numerical results confirmed the experimental ones where the pressure head loss for the triangular orifice is lower than the circular orifice and vena contracta is located at a distance equal to half the pipe diameter downstream of the orifice plate.
Flow through sharp-crested rectangular side orifices under free flow condition in open channels
Agricultural Water Management, 2011
Side orifices are widely used in irrigation and environmental engineering to spill or divert water from a channel. Flow characteristic of sharp-crested rectangular orifices under free flow condition in open channels is studied in the present paper. Existing discharge equations are checked for their accuracy using the data collected in the present study and available data in the literature and a new discharge equation has been proposed. The coefficient of discharge mainly depends on the approach flow Froude number and ratio of the size of orifice and bed width of the channel. Relationships for the coefficient of discharge, treating the orifice as large and small were developed. The computed discharges using these relationships were within ±5% of the observed ones. Measurement of three-dimensional velocities and visualisation of streamlines in a horizontal plane at the centerline of the orifice indicates that for the flow of low Froude number, almost all the streamlines divert towards the orifice. However, in the case of high Froude number flows, only those streamlines which are close to the side orifice are diverted towards the orifice. The opposite side of the boundary has significant effect on the diverted discharge of low Froude number compared to the flow of high Froude number. Circular orifice has been found to be more efficient compared to the rectangular orifice of the same opening area.
Determination of Orifice Coefficients for Flow Through Circular and Rectangular Orifices
ATBU Journal of Science, Technology and Education, 2018
Circular and rectangular orifices are among the types of orifices being classified according to geometrical shapes. They are among others widely used as flow meters. Knowledge about the orifice coefficients and discharges through circular and rectangular orifice is very important, when selection for use is based on the requirement of low or high discharges as well as high or low orifice coefficients. So, this research work experimentally determined the orifice coefficients and discharges through circular and rectangular orifices having the same area of 0.00015m 2 under a constant head of water of 0.9m. The experimental results revealed that under a constant head of water of 0.9m, circular orifice has average coefficient of discharge, coefficient of velocity, coefficient of contraction, theoretical and actual discharges as 0.62, 0.94, 0.66, 5.52x 10 -4 m 3 /s and 3.42x 10 -4 m 3 /s respectively. More so, that rectangular orifice under the same constant head of water of 0.9m, has a...
The effect of a plate installation upstream of an orifice on the pressurized flushing efficiency
Canadian Journal of Civil Engineering, 2022
The effect of a plate installation upstream of an orifice was investigated as a new method for improving the pressurized flushing efficiency. In this regard, a plate with three different widths () was installed at four different distances () upstream of the orifice. According to the results, the plate installation significantly increased the pressurized flushing efficiency due to the wake vortices formed upstream of the orifice. The flushing efficiency increased up to a maximum value of 11.5 times relative to what was calculated for the experiment without plate for the same conditions. For the best configuration of the plate width and its distance from the outlet (i.e., and , is the orifice diameter), the length, width, and depth of = 0.7 = 0.5 the flushing cone increased by about 160, 90, and 240% relative to the control experiment under the same conditions, respectively. Four empirical equations based on the effective and dimensionless variables were developed, enabling the users to have any predictions from the flushing cone volume and dimensions. Finally the importance of each effective parameters in the derived equations were analyzed using sensitivity analysis method. The sensitivity analysis results showed the greater impact of outlet discharge of the orifice and the plate distance than its width on the flushing cone volume and dimensions.
Effect of Varying Orifice Thickness on the Discharge Coefficient for Different Orifices Shapes
Engineering Research Journal - Faculty of Engineering (Shoubra)
One of the most important factors to be studied carefully is the discharge coefficient "Cd" through the orifices, which reflects the efficiency of the flow and plays an important role in the design of hydraulic units. The purpose of this paper is to investigate experimentally the effect of changing orifice thickness on the discharge coefficient for water flow through different orifice shapes and comparing each other. To achieve this goal, four orifices shapes were used: circular, square, equilateral triangle and rectangular, five different thicknesses (9.25, 7.5, 6.75, 4 and 2 mm) were tested. It should be noted that the tests were conducted on four different values of the pressure heads affecting the center of the hole: (35, 40, 45 and 50 cm). Bernoulli's equation was used as a theoretical basis for calculating the discharge coefficient. The results of the study demonstrated that the changing in the thickness of the orifice affects the coefficient of discharge. The coefficient of discharge gradually decreases when the ratio (orifice thickness "t"/orifice equivalent diameter "d") increases, with the fixity of both the orifice area and the vertical pressure head located above the center of the orifice. In all the analytical comparisons made in this study it was observed that circular orifices give the highest values of the coefficient of discharge compared to all other shapes followed by equilateral triangular orifices and then square orifices and finally it was observed that rectangular orifices give the lowest values of the coefficient of discharge.
Investigation of Flow Upstream of Orifices
Journal of Hydraulic Engineering, 2008
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Non-Newtonian Fluids Discharge Through Circular and Square Orifices from a Tank
2019
Orifices are commonly used to control and measure the discharge of Newtonian fluids from pipes, channels, reservoirs and tanks and are available in different types, shapes and sizes. The accuracy of non-Newtonian fluid flow rate measurements through orifices from tanks is not well understood with little research available on discharge of non-Newtonian fluids from circular orifices and not at all on square orifices. In this work, square and round orifices were used. Circular and square cross-section sharp crested orifices with similar hydraulic radii were fitted at the bottom of the tank. A rectangular tank suspended from a weighbridge fitted with a load cell was used to measure the rate of discharge. A rotary viscometer was used to establish the rheological parameters of the t est fluids. Water was used for calibration purpose. Different concentrations of glycerine and model non-Newtonian test fluids were used. From the experimental results, the coefficients of discharge (Cd) and or...
Discharge Coefficients for Orifices Cut into Round Pipes
Journal of Irrigation and Drainage Engineering, 2013
This study focuses on the discharge coefficient (C d) for flow into orifices cut with a circular bit perpendicular to and along the centerline of a round pipe, a common configuration on perforated risers installed as the principal outlets for stormwater detention or sediment basins. When predicting flow, the orifice area is generally defined as the area of the bit used to cut the hole, but the true orifice area is larger than the bit due to the curvature of the riser pipe. Four different descriptions for orifice area were tested while attempting to fit C d to measured discharge experiments. The tests showed that C d decreases as the orifice diameter approaches the diameter of the riser. Photographic imagery shows that the reduced C d is due to lateral flow from the riser's curved sides decreasing the vena contracta area more than what normally occurs during flow through an orifice in a flat plate. In contrast, but to a lesser extent, C d increases as the water surface approaches the top of the orifice. Best fit equations to model C d were developed to better estimate flow, with the most applicable having an R 2 of 88.8% and a root-mean squared error of 0.028. Orifice elevation above the tank floor was measured and initially modeled but was ultimately not included in the C d model because the R 2 improved by only 0.6%.