ArticlePDF Available

Theoretical Approaches Regarding the VENTURI Effect

Authors:

Abstract and Figures

In fluid mechanics there are situations when the fluid flow is carried out inside pipelines with different values of the main flow section. Based on the research works it was therefore demonstrated that when the fluid passes from a larger to a smaller section an increase in flow velocity is obtained together with a decrease of fluid static pressure. This phenomenon it is known as the VENTURI effect. This particular effect is based on both the fluid continuity principle, but also on the principle of conservation of mechanical energy, or BERNOULLI'S principle. This principle shows that inside a specific flow region, a decrease in static pressure appears when it is achieved an increase in fluid velocity. In this paper are presented the theoretical foundations regarding fluid flow inside a special model called the VENTURI tube where the effect can be emphasized. A three-dimensional model of the VENTURI tube was constructed with Solid Edge V20 and analyzed using ANSYS CFX for highlighting the fluid flow inside. The results are presented in terms of velocity and pressure of the working fluid.
Content may be subject to copyright.
ISSN 1453 7303 “HIDRAULICA” (No. 3/2016)
Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics
69
Theoretical Approaches Regarding the VENTURI Effect
Assistant professor Fănel Dorel ȘCHEAUA1
1) "Dunărea de Jos" University of Galați, fanel.scheaua@ugal.ro
Abstract: In fluid mechanics there are situations when the fluid flow is carried out inside pipelines with
different values of the main flow section. Based on the research works it was therefore demonstrated that
when the fluid passes from a larger to a smaller section an increase in flow velocity is obtained together with
a decrease of fluid static pressure. This phenomenon it is known as the VENTURI effect. This particular
effect is based on both the fluid continuity principle, but also on the principle of conservation of mechanical
energy, or BERNOULLI’S principle. This principle shows that inside a specific flow region, a decrease in
static pressure appears when it is achieved an increase in fluid velocity. In this paper are presented the
theoretical foundations regarding fluid flow inside a special model called the VENTURI tube where the effect
can be emphasized. A three-dimensional model of the VENTURI tube was constructed with Solid Edge V20
and analyzed using ANSYS CFX for highlighting the fluid flow inside. The results are presented in terms of
velocity and pressure of the working fluid.
Keywords: fluid flow, 3D modelling, computational fluid dynamics (CFD)
1. Introduction
In the XVII century Isaac Newton published his works related to the laws of motion. He is
considered the father of physics. Later in XVIII century Daniel Bernoulli published the fluid
mechanics principle that describes mathematically how the static pressure changes when fluid
flow rate is modifying in time. This principle describes an incompressible fluid flow and it is based
on the conservation of energy law.
The Italian physicist Giovanni Battista VENTURI (1746-1822) had made research works in the field
of fluid mechanics and published his results in 1797. These results are related to fluid flow inside a
constricted tube where he observed that the fluid motion is achieved with a higher velocity in the
region having small section area but in the same time with a smaller value recorded for static
pressure. In the region with a greater section area the fluid velocity was smaller while the static
pressure increased.
2. Daniel Bernoulli’s principle
The theoretical approaches that led to the principle formulated by Daniel Bernoulli in 1700's are
presented hereinafter.
Daniel Bernoulli published his research regarding fluid mechanics in 1738. He was a
mathematician that created a formula that mathematically explains how an increase in a fluid's flow
rate results in a decrease of static pressure exerted by that fluid. This equation is based on the
Law of Conservation of Energy. In order for the fluid to increase its speed, it must convert its
potential energy into kinetic energy. As kinetic energy (velocity) increases, potential energy (static
pressure) decreases. [2]
In a permanent flow regime of an ideally, incompressible fluid, subjected to the action of
conservative forces, Daniel Bernoulli's equation, as a load equation has the form: [4]
2
2
vp
zC
gγ
 
(1)
Where:
-
2
2
vg
- kinetic load;
ISSN 1453 7303 “HIDRAULICA” (No. 3/2016)
Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics
70
-
p
γ
- piezometric load;
-
- position load.
By multiplying equation (1) with fluid specific height and the fluid weight the pressure and energy
equation are obtained.
The Bernoulli equation describing the pressure values within an ideal incompressible fluid can be
written as: [4]
2
2st
ρv pγz C  
(2)
The energy equation can be written as: [4]
2
2st
ρv
G Gp Gγz C  
(3)
For a barotropic fluid (compressible), the Bernoulli equation as a load equation can be written as:
[4]
 
2
2
v dp zC
gγp
 
(4)
Along a fluid streamline the total pressure can be assumed as: [4]
2
2
st
ρv
pp
(5)
Where:
s
p
- static pressure;
2
2
ρv
- dynamic pressure.
3. VENTURI tube model CFD analysis
A model is constructed for the VENTURI tube and analyzed using ANSYS CFX in order to
emphasize the fluid flow parameters represented by air velocity and pressure.
Fig. 1. VENTURI tube mathematical model
For the two main fluid regions can be written: [3]
22
12
22
ss
ρv ρv
pp
   
 
   
   
(6)
It is expected that at the modification of fluid flow velocity through the tube interior pressure will
change its value in a certain region.
ISSN 1453 7303 “HIDRAULICA” (No. 3/2016)
Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics
71
The VENTURI tube model constructed was launched into numerical analysis using ANSYS CFX
software to observe the flow parameters of the working fluid (air) circulated through the tube. The
results are presented in terms of pressure and velocity of the working fluid, specific values being
recorded in different fluid regions within the analyzed model.
a) Imported model
b) Model mesh
Fig. 2. The VENTURI tube three-dimensional model
A mesh was achieved for the three-dimensional model of the VENTURI tube having a total of
25987 nodes and 21987 elements of tetrahedral form.
The analysis of fluid flow through the VENTURI tube was made for the air at 25 degrees Celsius,
with the declared static pressure value at the inlet in the range of (1.1, 1.3 and 1.9 bar), while the
reference pressure was 1 atm.
Three sets of values were obtained for the parameters that describe fluid flow through the tube
interior, being represented by pressure and velocity values on fluid regions. The obtained results
are presented for the three cases in the following.
a) The values for static pressure
b) Velocity values
Fig. 3. The obtained results for Case 1
a) The values for static pressure
b) Velocity values
Fig. 4. The obtained results for Case 2
ISSN 1453 7303 “HIDRAULICA” (No. 3/2016)
Magazine of Hydraulics, Pneumatics, Tribology, Ecology, Sensorics, Mechatronics
72
a) The values for static pressure
b) Velocity values
Fig. 5. The obtained results for Case 3
In Figures 3-5 are shown the values recorded for the static pressure and flow velocity of the
working fluid inside the tube being noted the high levels of the inlet pressure for the large diameter
section and the fluid velocity values are low. In the middle section the fluid velocity achieve high
values while the static pressure reaches low values.
TABLE 1: Diagrams of the fluid velocity and static pressure values for the three cases
Fluid velocity values [m/s]
0
10
20
30
40
Case 1
Case 2
Case 3
Case 1
37.83
28.38
18.92
9.459
Case 2
30.99
23.24
15.5
7.748
Case 3
28.38
21.28
14.19
7.094
1
2
3
4
Static pressure values [Pa]
-500000
-400000
-300000
-200000
-100000
0
100000
200000
300000
Case 1
Case 2
Case 3
Case 1
193100
1074
-190900
-382900
Case 2
132100
3335
-125400
-254200
Case 3
111800
3868
-104000
-211900
1
2
3
4
In Table 1 are presented the results diagrams for the three analyzed cases highlighting the
maximum and minimum static pressure and velocity values of fluid flow through the tube.
4. Conclusions
A three-dimensionally model of a VENTURI tube was achieved and analyzed in this paper. This
model can provide a solution to determine the fluid flow rate in a hydraulic or pneumatic installation
using manometers mounted on different sections of the tube. Based on different pressure values
recorded can be determined the flow rate for the working fluid circulated through the respective
section.
Also by means of the VENTURI tube can be achieved the mixture of two different fluids due to the
low pressure values recorded in the middle section where the fluid flow velocity values are high,
and as a result a fluid (which may be a liquid or gas) may be absorbed and transported further into
the hydraulic system circuit.
This property of making the mixture of two different fluids is used in automobile carburettors where
is realized the mixture of liquid fuel and air, or the development of the ejectors also using the
mixture of the two fluids.
References
[1] https://www.comsol.com/blogs/exploring-the-venturi-effect/
[2] https://answers.yahoo.com/question/index
[3] http://www.grc.nasa.gov/WWW/K 12/airplane/bern.html
[4] Vasilescu, Al., A., Mecanica fluidelor, Ministerul Educatiei și Învățământului, Universitatea din Galați,
Galați, 1979
... Chip1 generates low velocity jets (7-37 m/s) due to the lack of a tapered nozzle [18,60,27]. The tapering is present on chip2 resulting in higher velocities (17-67 m/s) [18,60,61]. Additionally, chip3 increases the maximum jet speed (77 m/s) due to the curved channel wall [18]. ...
Article
Hypothesis Needle-free injections using microfluidic jets could be optimized by reducing splashing and controlling injection depth. However, this is impeded by an incomplete understanding on how jet characteristics influence impact outcome. We hypothesise that exploring the relation between microfluidic jet characteristics and substrate shear modulus on impact characteristics will assist in predicting and giving insights on the impact outcome on skin. Experiments To do so, a setup using microfluidic chips, at varying laser powers and stand-off distances, was used to create thermocavitation generated microfluidic jets with ranging characteristics (speed: 7-77 m/s, diameter: 35-120 μm, Weber-number: 40-4000), which were impacted on substrates with varying shear modulus. Findings Seven impact regimes were found, depending on jet Weber-number and substrate shear modulus, and defined three thresholds: i) spreading/splashing threshold, ii) dimple formation threshold, and iii) plastic/elastic deformation threshold. The regimes show similarity to skin impact, although the opacity of skin complicated determining the threshold values. Additionally, we found that jet velocity has a higher predictive value for injection depth compared to the Weber-number, and consequently, the jet-diameter. Our findings provide fundamental knowledge on interaction between microfluidic jets and substrates, and are relevant for optimizing needle-free injections.
... The idea of ground effect widely depends on the Venturi effect [2], which is a physical effect regards on change of speed and pressure of fluid flowing through pipe with different clearance (cross section area) per section. Venturi effect can be described as following [3]: Assume certain fluid is flowing through a pipe shaped like the figure shown below. Assume the flow is steady, non-uniform flow, where the velocity of fluid differs per section but has constant inlet velocity. ...
Technical Report
Full-text available
CFD(Computational Fluid Dynamics) provides us an opportunity to analyze parameters of flow of fluids, heat transfer, chemical reactions of fluids using repetitive and continuous calculation processes that are performed in accordance with numerical analysis methods. Thus, CFD is widely used in design processes of ships, turbomachinery, energy generation facilities, and aircraft. [1] CFD is also commonly used in analysis of air flow that occurs over the surface of moving motor vehicles. Using these characteristics of CFD, the author adapted such method in analysis of ground effect of 'Neo 037', a vehicle designed by the author.
... Hay varios inconvenientes asociados a estas interfases, debido a que la cantidad de oxígeno suministrada no es suficiente para corregir la hipoxemia. La entrega de oxígeno suele ser limitada dado que el máximo flujo que se puede lograr es de 15 L/min en caso de la máscara y el oxígeno suministrado debe succionar aire del medioambiente, efecto Venturi, para que esta dilución de gases ingrese a la vía aérea (6). ...
Article
Full-text available
La pandemia por coronavirus tipo 2 o SARS-COV-2 tiene en jaque al sistema sanitario mundial dada su alta tasa de contagio; ha hecho colapsar todos los sistemas de salud y ha puesto en evidencia la escasez de recursos como los elementos de protección y la cantidad insuficiente de ventiladores en relación con el número de pacientes con falla respiratoria aguda hipoxémica. Por estas razones, se ha tenido que recurrir a diferentes opciones, una de ellas la cánula de alto flujo, que permite administrar oxígeno a alto flujo a los pacientes con hipoxemia severa. Durante la pandemia por COVID-19, se ha generado la inquietud acerca de que este dispositivo, como todos los dispositivos que permiten la administración de oxígeno, produce gran dispersión de aerosoles y la posibilidad de contagio del personal de la salud, lo cual ha llevado a desestimar su uso y utilizar de manera casi exclusiva la cánula nasal convencional y la ventilación mecánica en sujetos infectados. De manera que en este trabajo, se realizó una revisión de la literatura que recoge los mecanismos de acción, su seguridad para el personal de salud y las indicaciones del uso de la cánula nasal de alto flujo en los pacientes infectados por COVID-19 así como sus ventajas; entre ellas, ser dispositivo ahorrador de ventiladores mecánicos, lo que puede ser muy útil en el manejo de los pacientes en caso de un pico epidémico en Colombia.
... The venturi tube is a throttling differential pressure gauge that has been widely used in the flow measurement of single-phase or two-phase flow [21,22]. The submarine multiphase flowmeter, which was developed by Norway's ROXAR, uses a venturi-tube flowmeter combined with a gamma-ray densitometer to improve the accuracy of flow rates measurements [23]. It has the characteristics of accurate measurement, low energy consumption, stable performance, and convenient maintenance, and it has wide applications in the petrochemical industry [24,25]. ...
Article
Full-text available
In modern society, the oil industry has become the foundation of the world economy, and how to efficiently extract oil is a pressing problem. Among them, the accurate measurement of oil-gas two-phase parameters is one of the bottlenecks in oil extraction technology. It is found that through the experiment the flow patterns of the oil-gas two-phase flow will change after passing through the venturi tube with the same flow rates. Under the different oil-gas flow rate, the change will be diverse. Being motivated by the above experiments, we use the dual ECT sensors to collect the capacitance values before and after the venturi tube, respectively. Additionally, we use the linear projection algorithm (LBP) algorithm to reconstruct the image of flow patterns. This paper discusses the relationship between the change of flow patterns and the flow rates. Furthermore, a convolutional neural network (CNN) algorithm is proposed to predict the oil flow rate, gas flow rate, and GVF (gas void fraction, especially referring to sectional gas fraction) of the two-phase flow. We use ElasticNet regression as the loss function to effectively avoid possible overfitting problems. In actual experiments, we compare the Typical-ECT-imaging-based-GVF algorithm and SVM (Support Vector Machine) algorithm with CNN algorithm based on three different ECT datasets. Three different sets of ECT data are used to predict the gas flow rate, oil flow rate, and GVF, and they are respectively using the venturi front-based ECT data only, while using the venturi behind-based ECT data and using both these data.
Article
Full-text available
With the growing global warming and rise in pollution levels across the world in addition to several other factors such as deforestation, urbanization and ozone layer depletion, there has been a continuous increase in global rise in annual average temperature. Eco-cooler is a cheap and eco-friendly device made from non-biodegradable waste which can be used to reduce the indoor temperature of the building thus giving a comfortable living experience. Although a conventional design with symmetrical hole design is adopted in some under-developed countries as a commercial way, no study is being conducted for the improvement in performance of the Eco-cooler. Hence the present study has the main objective of evaluating different factors of dependency of an Eco-cooler, establishing them as a cheap and effective way of reducing indoor temperature and increasing its efficiency.
Article
Full-text available
Flexible printed electronic circuits have recently attracted attention as an alternative promising methodology due to the additive process being more environmentally friendly and using less raw material compared to conventional lithography and chemical vapor deposition. However, printed circuits produced by roll-to-roll (R2R) conveyance are often scratched, which can result in breaks in the conductive tracks, cracks, or pinholes. This study investigated a proposed optimal design for an air bar for use in an R2R printing system. The optimal distance between the roll surface and floating substrate for preventing scratching of the printed circuit was investigated. The optimal design—including the blower frequency, size of air holes, and density of air holes—was investigated using simulations of fluid–structure interactions for estimating substrate behavior during pneumatic flotation. The distribution of air pressure in the space between the substrate and the surface of the air bar was calculated, and the deformation of the substrate by the air pressure was analyzed. The optimal design of the air bar was verified in numerical simulations and experiments using various conditions.
Conference Paper
Full-text available
The axial propeller pumps represent the volumetric units that achieves driving and circulation of a working fluid through a duct. This type of hydraulic unit is capable of directing the working fluid in the axial direction within the pipeline ensuring a considerably flow rate in time, having also the possibility of modifying the flow rate by adjusting the position of the propeller blades that acts directly on the working fluid. The axial propeller pumps are part of hydrodynamic or kinetic pumps that converts mechanical energy taken at pump shaft from an electric or thermal motor into kinetic energy of the working fluid characterized by mass flow rate and flow velocity. In this paper it is analyzed an axial propeller pump model in order to highlight the flow parameters at circulation of working fluid inside due to the rotational movement of the propeller blades.
Mecanica fluidelor, Ministerul Educatiei și Învățământului
  • Al Vasilescu
Vasilescu, Al., A., Mecanica fluidelor, Ministerul Educatiei și Învățământului, Universitatea din Galați, Galați, 1979