Group learning challenge 1 Figure out how much the flow rate through a porous media will change for a 5 C change in temperature. Does flow rate increase or decrease as temperature increases

Group learning challenge 2. Figure out an approximate height of capillary rise (the height of the capillary fringe) in sand with average pore size approximated as 0.05 mm Figure out an approximate height of capillary rise (the height of the capillary fringe) in silt with average pore size of 0.005 mm Force due to surface tension around the circumference of the tube is 𝐹=2𝜋𝑟 𝜎 Pressure is this force over the area 𝑃= 𝐹 𝐴 = 2𝜋𝑟 𝜎 𝜋 𝑟 2 = 2 𝜎 𝑟 This corresponds to a pressure head 𝜓= 𝑃 𝜌𝑔 = 2 𝜎 𝑟𝜌𝑔 For r=0.05 mm and at 20 C, =7.28 x 10-2 N/m 𝜓= 2 ×7.28 × 10 −2 𝑁/𝑚 5× 10 −5 𝑚 ×1000 𝑘𝑔 𝑚 −3 ×9.81 𝑚/𝑠^2 =0.29 𝑚=29 𝑐𝑚 R: 2*7.28e-2/(5e-5*1000*9.81) 0.29684 This is how much water will be sucked up into sand by capillary surface tension forces. For silt r=0.005 mm 𝜓= 2 ×7.28 × 10 −2 𝑁/𝑚 5× 10 −6 𝑚 ×1000 𝑘𝑔 𝑚 −3 ×9.81 𝑚/𝑠^2 =2.9 𝑚=290 𝑐𝑚 R: 2*7.28e-2/(5e-6*1000*9.81) 2.9684 This is fairly small in sand but nearly 3 m in silt. Note that these are upper bounds as these pore size values are at the lower limit of the pore size ranges for sand and silt.