Question

ADD TO HW: Use of Darcy law under unsteady conditions: 11111 I H=H2 - H dz/dt Vp= dz/dt Z H2 Soil, K, n Vp = VDarcy/n gravel impervious

asked my professor for the question and havent gotten a response

Answer 1

Darcy law under unsteady conditions (i) The Darcy Law is valia in case of Linear laminar How through saturated porous media. (ii) Although this law is widely used, it is not valia in the case of laminar unsteady or Cydic flow due to the action of shart waves within soil ana eart structures, which can affect their behaviour and durability. (111) The extension of Darcy law can be suitable for unsteady flows by deriving from Navierstokes equations combined with with capillary type model. I) In order to validate these models an experimental device simulating flows Que to shart waves within soil can be developed. (V) The results obtained from these test shows that the effects of accleration generates an increase of interstitial pressure within the soils. (vi) We can observe that, the flow velocity is proportional to hydraulic gradient as long as the flow is laminar (shown by section (I) in ti gure below) (vid As the velocity is increased further, a critical stage is reached at which eaaies begin to form hear the wall

of the tube and the relationship between flow velocity and by araulic velocity becomes uncertain (shown by section (II) infigure below). (viis) A further increase in velocity again leads to a definite relationship, this time, vepresentea by a continuous curved line C shown by sectiom tu (x) once in the turbulent zone, if the velocity is aecreased, the How remain turbulent well into tronsition (zone. II) until the motion reverts to Laminar How. Transition (I) 4/ Turbulent Hydraulic gradient (i) Laminas' (I) (11) Ver Flow velocity figures - 2o Laminar ana turbulent flow