Well fluid mechanics( Well hydraulics )

Well hydraulics or well fluid mechanic is an important part of ground water engineering. Groundwater withdrawal from aquifer are more important to meet the demand. Therefore we need to understand the well hydraulics or well fluid mechanics.

Steady Radial Flow to a Well

When farmer pumps well, the pump removes water from the geological formation of close the well, and also the geological formation or piezometric surface, betting on the sort of geological formation, is lowered. The drawdown at a given purpose is that the distance the water level is down. A drawdown curve (or cone) shows the variation of drawdown with distance from the well. In 3 dimensions, the drawdown curve describes a conic form called the cone of depression. The outer limit of the cone of depression (zero drawdown) defines the world of influence of the well. Steady Radial Flow to a Well during a Confined geological formation

(Dupuit 1863, later changed by Thiem, 1906)

The assumption equations of well hydraulics (well fluid mechanics):

The assumptions within the Thiem’s equations are:

Stabilized Drawdown.
Constant thickness of the geological formation with constant permeableness (isotropic).
Complete penetration of the well with 100% potency.
Radial flow into the well…………… (i)

Rearranging and desegregation equation (i) for the stipulation at the well, h=hw and r=rw and at the sting of the geological formation h=h0 and r= r0 (with the negative sign neglected),

Q = 2πKb

or, alphabetic character ln  = 2πKb

or, Q = 2πKb    ……… (ii)

In the additional general case of a well penetrating an in depth confined geological formation as shown in Figure a pair of, there’s no external limit for ‘r’. From the equation (ii) at any given worth of ‘r’,

Q = 2πKb  ………. (iii)

The equation (iii) is thought as equilibrium or Thiem equation, allows the hydraulic conduction or the transmissivity of a confined geological formation to be determined from a tense well. The equation (iii) may also be written in traditional exponent as:

In well fluid mechanics Theory:

Theoretically,

hw at the tense well will function one measuring point; but, well losses caused by flow through the well screen and within the well introduce errors in order that hw ought to be avoided. The transmissivity is given by,

T = kilobyte =  ln  …….. (iv)

Where, r1 and r2 ar the distances and h1 and h2 ar the heads of the several observation wells.

From the sensible posture, the drawdown s instead of the pinnacle h is measured in order that the equation (iv) may be written as:

T =  ln  ……….. (v)

The equation (iii) may also be written in traditional exponent as:

Q =   ………… (vi)

or, Q =   ………. (vii)

or, K=  …………. (viii)

Where, alphabetic character is in Gallons/minute, K is that the Hydraulic conduction in Gallons/day/sq.ft. and r and h ar measured in feet and b is thickness of geological formation.

Example 1:

Example 2:

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