Hardy cross method

SOLUTION TO A SIMPLE PIPE NETWORK DISTRIBUTION PROBLEM USING

HARDY CROSS METHOD

• The method suggests that the flow in each pipe in magnitude and direction is to be initially ASSUMED in such a way that the principle of continuity is satisfied at each junction
• A correction to the assumed flows is computed successively for each pipe loop in the network until the correction is reduced to an acceptable magnitude. (Normally two iterations are sufficient)
• According to the principle of continuity the inflow at any junction is equal to the outflow at that junction
• As the method involves balancing quantities of inflow and outflow at each junction, it is also called quantity balance method
• Value of 'x' in Hardy-Cross method is assumed to be 1.85 for 'Hazen-William's' formula and 2 for Darcy-Weisbach formula.
• Minor losses are generally neglected
• The system should be divided into two or more loops such that each pipe in the network is included in at-least one loop

SUMMARIZING THE HARDY CROSS METHOD

• Assume any internally consistent distribution of flow
• Compute head loss in each pipe (clockwise flows are positive and produce positive head loss and vice versa)
• Paying attention to sign, compute the total head loss around each loop is computed.
• Compute the total head loss around each loop regardless of sign
• Apply corrections to the flow in each pipe