Fluid flow measuring devices and methods for determining fluid flow rates in soils

A fluid flow measuring device for determining unsaturated fluid flow rates in below grade earthen soils, comprising:

• a conduit for receiving a fluid which is traveling under the influence of gravity and in a generally vertical direction downwardly through the below grade earthen soil and at a fluid flow rate of less than about 1000 millimeters per year, and wherein the conduit is substantially vertically oriented and lies in immediate contact with the below grade earthen soil, and wherein the conduit comprises a converging conical section which receives below grade earthen soil and which is further operable to receive the fluid which is traveling in the generally vertical direction downwardly through the below grade earthen soil, a diverging conical section disposed in spaced relation relative to the converging conical section, and a channel portion which has a diametral dimension of about 0.6 centimeters, and which has an upstream end which is coupled in fluid communication to the converging conical section, and an opposite downstream end which is coupled in fluid flowing communication with the diverging conical section, and wherein the conduit is operable to receive the fluid which is traveling substantially downwardly under the influence of gravity, and to amplify the fluid flow rate of the fluid by at least one order of magnitude;
• a porous medium mounted in substantially occluding relation relative to the upstream end of the channel portion, and which allows the passage of the fluid which is traveling substantially vertically downwardly under the influence of gravity, and which further substantially produces a substantially laminar fluid flow of the fluid in the channel portion, and wherein the porous medium substantially prohibits the entry of the below grade earthen soil into the channel portion;
• a heater borne by the channel portion and which is operable to impart heat energy to the substantially laminar flow of fluid traveling substantially vertically downwardly through the channel portion;
• a first temperature sensor borne by the channel portion and which is located in temperature sensing relation relative to the substantially laminar flow of fluid, and which is further oriented in spaced, upstream relation relative to the heater, and wherein the first temperature sensor is substantially thermally isolated from the surrounding earthen soil which lies in contact with the channel portion;
• a second temperature sensor borne by the reduced channel portion and which is located in temperature sensing relation relative to the substantially laminar flow of the fluid, and which is further oriented in spaced, downstream relation relative to the heater, and wherein the second temperature sensor is substantially thermally isolated from the surrounding earthen soil which lies in contact with the channel portion, and wherein a temperature differential is established in the substantially laminar fluid flow in the channel portion and which is measured by the first and second temperature sensors;
• and
• a data logger and display positioned above grade, and which are electrically coupled with each of the heater and the first and second temperature sensors, and wherein the data logger and the display calculate from the temperature differential the amplified fluid flow rate of the substantially laminar flow moving substantially vertically downwardly through the channel portion.