Numerical Study of Nutrient Mixing in Trabecular Bone in Microgravity, Disuse and Normogravity

<p>Mechanical loading is known to regulate bone remodeling by driving interstitial fluid flow which stimulates cells and drives nutrient transport within the trabecular network. In microgravity, the absence of mechanical stimulation or loading suppresses convective flow processes, causing diffusion-driven nutrient mixing and renewal, and accelerated bone loss. This thesis investigates how oscillation frequency and trabecular bone density jointly control nutrient mixing and wall shear stress within trabecular cavities.</p> <p>A computational fluid dynamics (CFD) framework is developed in STAR-CCM+ using a soft-cap oscillation model that mimics cyclic compression. Three idealized trabecular morphologies are simulated across different frequencies to represent microgravity or disuse, walking, and running conditions. Scalar concentration decay is quantified using the spatial root-mean-square metric and fitted with a bi-exponential model representing diffusive and convective mixing phases.</p> <p>Results show that nutrient mixing occurs in two stages: an initial diffusion-dominated rapid mixing phase followed by a convection-driven slow decay phase as oscillatory flow structures develop. Increasing frequency enhances convective transport, reduces mixing time, and elevates wall shear stress into the osteogenic range. In diffusion-influenced regimes, lower bone density facilitates deeper-stage homogenization due to greater pore connectivity, whereas in convection-dominated regimes higher bone density intensifies recirculation through confinement-induced velocity amplification. The bi-exponential rate constants show dependencies on frequency and bone density. Viscosity variations within the physiological marrow range show negligible influence on global mixing behavior, but significantly affect the shear stress experienced by the bone cells.</p> <p>These findings establish oscillation frequency and trabecular morphology as dominant parameters governing marrow-level nutrient renewal. For shear stress on the cells, all three of the parameters i.e., frequency, bone density and viscosity, show a significant impact. The derived decay models and shear–mixing relationships provide a mechanistic basis for designing mechanical countermeasures, such as low-magnitude, high-frequency vibration, to sustain osteocyte activity and mitigate bone loss under microgravity and mechanical disuse conditions.</p>

Name thesis:degree_name

Master of Science in Aerospace Engineering

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Aerospace Engineering

Year

2026

Author dc:creator

• Gharti, Sagar

• microgravity
• osteoporosis
• computational fluid dynamics
• CFD
• nutrient mixing
• bone mechanobiology
• nutrient transport
• convection-diffusion
• biological phenomena
• biofluids
• Aerodynamics and Fluid Mechanics
• Biomechanical Engineering
• Biomechanics and Biotransport
• Computational Engineering
• Fluid Dynamics
• Space Habitation and Life Support
• Transport Phenomena

Repository record dc:identifier

https://commons.erau.edu/edt/956

OAI identifier oai:identifier

oai:commons.erau.edu:edt-2000