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Hydraulic elements in series
Storyboard 
When hydraulic elements are connected in series, the flow remains constant, but each hydraulic element experiences a pressure drop. The sum of these pressure drops equals the total drop, and therefore, the total hydraulic resistance is equal to the sum of all individual hydraulic resistances. On the other hand, the inverse of the total hydraulic conductivity is equal to the sum of the inverses of the hydraulic conductivities.
ID:(1466, 0)
Hydraulic resistance of elements in series
Concept
In the case of a sum where the elements are connected in series, the total hydraulic resistance of the system is calculated by summing the individual resistances of each element.
One way to model a tube with varying cross-section is to divide it into sections with constant radius and then sum the hydraulic resistances in series. Suppose we have a series of the hydraulic resistance in a network ($R_{hk}$), which depends on the viscosity ($\eta$), the cylinder k radio ($R_k$), and the tube k length ($\Delta L_k$) via the following equation:
| $ R_{hk} =\displaystyle\frac{8 \eta | \Delta L_k | }{ \pi R_k ^4}$ |
In each segment, there will be a pressure difference in a network ($\Delta p_k$) with the hydraulic resistance in a network ($R_{hk}$) and the volume flow ($J_V$) to which Darcy's Law is applied:
| $ \Delta p_k = R_{hk} J_V $ |
the total pressure difference ($\Delta p_t$) will be equal to the sum of the individual pressure difference in a network ($\Delta p_k$):
| $ \Delta p_t =\displaystyle\sum_k \Delta p_k $ |
therefore,
$\Delta p_t=\displaystyle\sum_k \Delta p_k=\displaystyle\sum_k (R_{hk}J_V)=\left(\displaystyle\sum_k R_{hk}\right)J_V\equiv R_{st}J_V$
Thus, the system can be modeled as a single conduit with the hydraulic resistance calculated as the sum of the individual components:
| $ R_{st} =\displaystyle\sum_k R_{hk} $ |
ID:(3630, 0)
Hydraulic conductance of elements in series
Concept
In the case of a sum where the elements are connected in series, the total hydraulic conductance of the system is calculated by adding the individual hydraulic conductances of each element.
the total hydraulic resistance in series ($R_{st}$), along with the hydraulic resistance in a network ($R_{hk}$), in
| $ R_{st} =\displaystyle\sum_k R_{hk} $ |
and along with the hydraulic conductance in a network ($G_{hk}$) and the equation
| $ R_{hk} = \displaystyle\frac{1}{ G_{hk} }$ |
leads to the total Series Hydraulic Conductance ($G_{st}$) can be calculated with:
| $\displaystyle\frac{1}{ G_{st} }=\displaystyle\sum_k\displaystyle\frac{1}{ G_{hk} }$ |
$\Delta p_k = \displaystyle\frac{J_{Vk}}{K_{hk}}$
So, the sum of the inverse of the hydraulic conductance in a network ($G_{hk}$) will be equal to the inverse of the total Series Hydraulic Conductance ($G_{st}$).
ID:(11067, 0)
Process for the addition of hydraulic resistances in series
Description
First, values for the hydraulic resistance in a network ($R_{hk}$) are calculated using the variables the viscosity ($\eta$), the cylinder k radio ($R_k$), and the tube k length ($\Delta L_k$) through the following equation:
| $ R_{hk} =\displaystyle\frac{8 \eta | \Delta L_k | }{ \pi R_k ^4}$ |
These values are then summed to obtain the total hydraulic resistance in series ($R_{st}$):
| $ R_{st} =\displaystyle\sum_k R_{hk} $ |
With this result, it is possible to calculate the volume flow ($J_V$) for the total pressure difference ($\Delta p_t$) using:
| $ \Delta p_t = R_{st} J_V $ |
Once the volume flow ($J_V$) is determined, the pressure difference in a network ($\Delta p_k$) is calculated via:
| $ \Delta p_k = R_{hk} J_V $ |
For the case of three resistances, the calculations can be visualized in the following chart:
ID:(11069, 0)
Model
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$\displaystyle\frac{1}{ G_{st} }=\displaystyle\sum_k\displaystyle\frac{1}{ G_{hk} }$
1/ G_st = @SUM( 1/ G_hk, k )
$ \Delta p_t = R_{st} J_V $
Dp = R_h * J_V
$ \Delta p_k = R_{hk} J_V $
Dp = R_h * J_V
$ \Delta p_t =\displaystyle\sum_k \Delta p_k $
Dp_t =sum_k Dp_k
$ G_{hk} =\displaystyle\frac{ \pi R_k ^4}{8 \eta | \Delta L_k | }$
G_h = pi * R ^4/(8* eta * abs( DL ))
$ J_V = G_{st} \Delta p_t $
J_V = G_h * Dp
$ J_V = \Delta p_k G_{hk} $
J_V = G_h * Dp
$ R_{st} = \displaystyle\frac{1}{ G_{st} }$
R_h = 1/ G_h
$ R_{hk} = \displaystyle\frac{1}{ G_{hk} }$
R_h = 1/ G_h
$ R_{hk} =\displaystyle\frac{8 \eta | \Delta L_k | }{ \pi R_k ^4}$
R_h =8* eta * abs( DL )/( pi * R ^4)
$ R_{st} =\displaystyle\sum_k R_{hk} $
R_st =@SUM( R_hk , k )
ID:(15732, 0)
Darcy's law and hydraulic resistance (1)
Equation
Darcy rewrites the Hagen Poiseuille equation so that the pressure difference ($\Delta p$) is equal to the hydraulic resistance ($R_h$) times the volume flow ($J_V$):
| $ \Delta p_t = R_{st} J_V $ |
| $ \Delta p = R_h J_V $ |
The volume flow ($J_V$) can be calculated from the hydraulic conductance ($G_h$) and the pressure difference ($\Delta p$) using the following equation:
| $ J_V = G_h \Delta p $ |
Furthermore, using the relationship for the hydraulic resistance ($R_h$):
| $ R_h = \displaystyle\frac{1}{ G_h }$ |
results in:
| $ \Delta p = R_h J_V $ |
ID:(3179, 1)
Darcy's law and hydraulic resistance (2)
Equation
Darcy rewrites the Hagen Poiseuille equation so that the pressure difference ($\Delta p$) is equal to the hydraulic resistance ($R_h$) times the volume flow ($J_V$):
| $ \Delta p_k = R_{hk} J_V $ |
| $ \Delta p = R_h J_V $ |
The volume flow ($J_V$) can be calculated from the hydraulic conductance ($G_h$) and the pressure difference ($\Delta p$) using the following equation:
| $ J_V = G_h \Delta p $ |
Furthermore, using the relationship for the hydraulic resistance ($R_h$):
| $ R_h = \displaystyle\frac{1}{ G_h }$ |
results in:
| $ \Delta p = R_h J_V $ |
ID:(3179, 2)
Hydraulic resistance of a tube
Equation
Since the hydraulic resistance ($R_h$) is equal to the inverse of the hydraulic conductance ($G_h$), it can be calculated from the expression of the latter. In this way, we can identify parameters related to geometry (the tube length ($\Delta L$) and the cylinder radio ($R$)) and the type of liquid (the viscosity ($\eta$)), which can be collectively referred to as a hydraulic resistance ($R_h$):
| $ R_{hk} =\displaystyle\frac{8 \eta | \Delta L_k | }{ \pi R_k ^4}$ |
| $ R_h =\displaystyle\frac{8 \eta | \Delta L | }{ \pi R ^4}$ |
Since the hydraulic resistance ($R_h$) is equal to the hydraulic conductance ($G_h$) as per the following equation:
| $ R_h = \displaystyle\frac{1}{ G_h }$ |
and since the hydraulic conductance ($G_h$) is expressed in terms of the viscosity ($\eta$), the cylinder radio ($R$), and the tube length ($\Delta L$) as follows:
| $ G_{hk} =\displaystyle\frac{ \pi R_k ^4}{8 \eta | \Delta L_k | }$ |
we can conclude that:
| $ R_h =\displaystyle\frac{8 \eta | \Delta L | }{ \pi R ^4}$ |
ID:(3629, 0)
Sum of series pressures
Equation
The total pressure difference ($\Delta p_t$) in relation to the various pressure difference in a network ($\Delta p_k$), leading us to the following conclusion:
| $ \Delta p_t =\displaystyle\sum_k \Delta p_k $ |
ID:(4377, 0)
Hydraulic resistance of elements in series
Equation
When there are multiple hydraulic resistances connected in series, we can calculate the total hydraulic resistance in series ($R_{st}$) by summing the hydraulic resistance in a network ($R_{hk}$), as expressed in the following formula:
| $ R_{st} =\displaystyle\sum_k R_{hk} $ |
One way to model a tube with varying cross-section is to divide it into sections with constant radius and then sum the hydraulic resistances in series. Suppose we have a series of the hydraulic resistance in a network ($R_{hk}$), which depends on the viscosity ($\eta$), the cylinder k radio ($R_k$), and the tube k length ($\Delta L_k$) via the following equation:
| $ R_{hk} =\displaystyle\frac{8 \eta | \Delta L_k | }{ \pi R_k ^4}$ |
In each segment, there will be a pressure difference in a network ($\Delta p_k$) with the hydraulic resistance in a network ($R_{hk}$) and the volume flow ($J_V$) to which Darcy's Law is applied:
| $ \Delta p_k = R_{hk} J_V $ |
the total pressure difference ($\Delta p_t$) will be equal to the sum of the individual pressure difference in a network ($\Delta p_k$):
| $ \Delta p_t =\displaystyle\sum_k \Delta p_k $ |
therefore,
$\Delta p_t=\displaystyle\sum_k \Delta p_k=\displaystyle\sum_k (R_{hk}J_V)=\left(\displaystyle\sum_k R_{hk}\right)J_V\equiv R_{st}J_V$
Thus, the system can be modeled as a single conduit with the hydraulic resistance calculated as the sum of the individual components:
| $ R_{st} =\displaystyle\sum_k R_{hk} $ |
ID:(3180, 0)
Hydraulic conductance (1)
Equation
In the context of electrical resistance, there exists its inverse, known as electrical conductance. Similarly, what would be the hydraulic conductance ($G_h$) can be defined in terms of the hydraulic resistance ($R_h$) through the expression:
| $ R_{st} = \displaystyle\frac{1}{ G_{st} }$ |
| $ R_h = \displaystyle\frac{1}{ G_h }$ |
ID:(15092, 1)
Hydraulic conductance (2)
Equation
In the context of electrical resistance, there exists its inverse, known as electrical conductance. Similarly, what would be the hydraulic conductance ($G_h$) can be defined in terms of the hydraulic resistance ($R_h$) through the expression:
| $ R_{hk} = \displaystyle\frac{1}{ G_{hk} }$ |
| $ R_h = \displaystyle\frac{1}{ G_h }$ |
ID:(15092, 2)
Hydraulic Conductance of a Pipe
Equation
With the cylinder radio ($R$), the viscosity ($\eta$) and the tube length ($\Delta L$) we have that a hydraulic conductance ($G_h$) is:
| $ G_{hk} =\displaystyle\frac{ \pi R_k ^4}{8 \eta | \Delta L_k | }$ |
| $ G_h =\displaystyle\frac{ \pi R ^4}{8 \eta | \Delta L | }$ |
ID:(15102, 0)
Darcy's law and hydraulic conductance (1)
Equation
With the introduction of the hydraulic conductance ($G_h$), we can rewrite the Hagen-Poiseuille equation with the pressure difference ($\Delta p$) and the volume flow ($J_V$) using the following equation:
| $ J_V = G_{st} \Delta p_t $ |
| $ J_V = G_h \Delta p $ |
If we examine the Hagen-Poiseuille law, which allows us to calculate the volume flow ($J_V$) from the cylinder radio ($R$), the viscosity ($\eta$), the tube length ($\Delta L$), and the pressure difference ($\Delta p$):
| $ J_V =-\displaystyle\frac{ \pi R ^4}{8 \eta }\displaystyle\frac{ \Delta p }{ \Delta L }$ |
we can introduce the hydraulic conductance ($G_h$), defined in terms of the tube length ($\Delta L$), the cylinder radio ($R$), and the viscosity ($\eta$), as follows:
| $ G_{hk} =\displaystyle\frac{ \pi R_k ^4}{8 \eta | \Delta L_k | }$ |
to arrive at:
| $ J_V = G_h \Delta p $ |
ID:(14471, 1)
Darcy's law and hydraulic conductance (2)
Equation
With the introduction of the hydraulic conductance ($G_h$), we can rewrite the Hagen-Poiseuille equation with the pressure difference ($\Delta p$) and the volume flow ($J_V$) using the following equation:
| $ J_V = \Delta p_k G_{hk} $ |
| $ J_V = G_h \Delta p $ |
If we examine the Hagen-Poiseuille law, which allows us to calculate the volume flow ($J_V$) from the cylinder radio ($R$), the viscosity ($\eta$), the tube length ($\Delta L$), and the pressure difference ($\Delta p$):
| $ J_V =-\displaystyle\frac{ \pi R ^4}{8 \eta }\displaystyle\frac{ \Delta p }{ \Delta L }$ |
we can introduce the hydraulic conductance ($G_h$), defined in terms of the tube length ($\Delta L$), the cylinder radio ($R$), and the viscosity ($\eta$), as follows:
| $ G_{hk} =\displaystyle\frac{ \pi R_k ^4}{8 \eta | \Delta L_k | }$ |
to arrive at:
| $ J_V = G_h \Delta p $ |
ID:(14471, 2)
Hydraulic conductancia of elements in series
Equation
In the case of hydraulic resistances in series, the inverse of the total Series Hydraulic Conductance ($G_{st}$) is calculated by summing the inverses of each the hydraulic conductance in a network ($G_{hk}$):
| $\displaystyle\frac{1}{ G_{st} }=\displaystyle\sum_k\displaystyle\frac{1}{ G_{hk} }$ |
The total hydraulic resistance in series ($R_{st}$), along with the hydraulic resistance in a network ($R_{hk}$), in
| $ R_{st} =\displaystyle\sum_k R_{hk} $ |
and along with the hydraulic conductance in a network ($G_{hk}$) and the equation
| $ R_{hk} = \displaystyle\frac{1}{ G_{hk} }$ |
leads to the total Series Hydraulic Conductance ($G_{st}$) can be calculated with:
| $\displaystyle\frac{1}{ G_{st} }=\displaystyle\sum_k\displaystyle\frac{1}{ G_{hk} }$ |
ID:(3633, 0)