The main objective of this investigation is to study experimentally the water surface
profiles and to obtain convenient expressions for the estimation of discharge
coefficients (Cd) for free flow over chimney weir and the discharge factor (q/q1) for
submerged flow. Four chimney weir models with different vertex angles were
constructed and tested, the surface water profiles, for all models were smooth upstream
and fall suddenly downstream the model and at a high discharge it become concave
while at law discharge the water surface profile become convex. The coefficient of
discharge for free flow increase with the decrease of the upstream head and with the
decrease of half vertex angle (θ ). While the discharge factor for submerged flow
increase with the decrease of the submergence ratio (h2/h1). Two general expressions
were optioned, one, for the estimation of Cd with respect of (h/p),(w/p) and θ for free
flow conditions and the other for estimation of the coefficient factor (q/q1) with respect
to (h2/h1) and (h1/p).