Abstract:Some hydropower stations were built on soluble rocks such as carbonate and the flow field

chemical field and solid properties around a dam site were changed

which may have adverse effect on the operation.Two factors

surface reaction and mass transfer

were thought to control the dissolution process.Based on this

a model of coupled fluid flow and chemical dissolution in a single fracture was built up and solved.And the results showed that the dissolution front is not a plane

but somehow like wormholes.And the aperture along the fracture becomes narrower.Although the flow through the fracture becomes larger

the amplitude was small.And the range and growth rate of equivalent hydraulic aperture are much smaller than actual average aperture.The distribution of Ca2+concentration is similar to the aperture

while the reaction rate at upstream is much faster than the one at downstream.And along the whole fracture it is controlled by surface reaction initially. As the dissolution processing

it turns to mass transfer control near the inlet

while it remains surface reaction controlled near the downstream.