Presentation on theme: "Soil Physics 2010 Outline More Wikipedia stuff Where were we? Kinds of models Mass and Volume."— Presentation transcript:
Soil Physics 2010 Outline More Wikipedia stuff Where were we? Kinds of models Mass and Volume
Soil Physics 2010 Wikipedia stuff 3 (out of 16) students have now claimed topics. Don’t be left out! Avoid the rush! On Monday, Jan 25, I will start assigning topics to students who have not yet chosen their own.
Soil Physics 2010 1: Give one example each of a: (a) Fibrous porous medium (b) Granular porous medium (c) Foam porous medium Extra points if all 3 naturally occur in soils. wood, fibrous plant material, fungal hyphae, plant roots sand, silt, soil solids pumice, tuff, vessiculated basalt, Quiz
Soil Physics 2010 Quiz 2: A soil has porosity = 0.33, and particle density s = 2700 kg m -3. What is its bulk density ( b )? Method 1 – just reasoning through the problem: Consider a cubic meter of this soil. If it had zero porosity, it would mass 2700 kg. But 1/3 of it is air, so it must mass (2/3)*2700 = 1800 kg. It’s a cubic meter, so its bulk density is b = 1800 kg m -3.
Soil Physics 2010 Quiz 2: A soil has porosity = 0.33, and particle density s = 2700 kg m -3. What is its bulk density ( b )? Method 2: drawing on the assigned reading Hillel gives an example showing Solving for b gives, so b = (2/3)*2700 kg/m 3 = 1800 kg/m 3
Porous implies Pores: What’s a pore? The porespace is typically multiply connected: each pore connects to several others. A complete description of the porespace must have both geometrical (size) and topological (connectivity) components. Soil Physics 2010 After K.K. Mohanty, 1980 Where were we?
Irwin Fatt said (Petr. Trans. AIME, 1956) : What are the available models for porous media? Soil Physics 2010 Capillary tubes are too simplistic – they’re singly connected Glass beads are intractable, and they’re still too simple.
Kinds of models What is a model? Soil Physics 2010
What is a model? A representation of reality A simplified representation or description A physical, mathematical, or otherwise logical representation of a system, real world entity, phenomenon, or process A representation of a process or system that attempts to relate the most important variables in the system in such a way that analysis of the model leads to insights into the system
Soil Physics 2010 Conceptual models All models start as conceptual models: “Think of the soil as a sandpile” “Imagine that this soil is a sponge” “What if all the pores in this soil were the same size?”