ORCID Number
0009-0005-5759-9944
Date of Award
Summer 8-2026
Embargo Period
8-6-2027
Access Type
Dissertation - Open Access
Degree Name
Doctor of Philosophy in Aerospace Engineering
Department
Aerospace Engineering
Committee Chair
Ebenezer Gnanamanickam
Committee Chair Email
gnanamae@erau.edu
Committee Advisor
Ebenezer Gnanamanickam
Committee Advisor Email
gnanamae@erau.edu
First Committee Member
Anastasios S. Lyrintzis
First Committee Member Email
lyrintzi@erau.edu
Second Committee Member
Surabhi Singh
Second Committee Member Email
singhs36@erau.edu
Third Committee Member
Birce Dikici
Third Committee Member Email
dikicib@erau.edu
College Dean
James W. Gregory
Abstract
Solid-gas two-phase flows are a ubiquitous phenomenon encountered in several processes, both engineered and natural. The present work investigated two aspects of solid-gas flows. First, the specific scales contributing to incipient motion were examined. Following this, the interaction between the carrier-phase and already mobilized particles was investigated. An experimental framework was developed to study the initiation of particle mobilization in a laboratory setting. An airfoil oscillated in the free-stream, generating a tonal free-stream disturbance that perturbed a turbulent boundary layer and increased the energy along specific scales. The size of this flow scale was shown to be controlled by changing the frequency of oscillation, while the energy in this flow scale was controlled via the amplitude of oscillation. The flow developing behind this forced flow was characterized using hot-wire anemometry and particle image velocimetry (PIV). Following this, measurements were carried out in which this forced carrier-phase flow mobilized large and heavy particles nominally resting on a particle bed. A PIV-based approach was used to measure the initiation of particle motion as well as the incoming carrier-phase velocity field. Qualitative observations across several oscillation profiles demonstrated that mobilization was highly intermittent and robustly correlated with the large-scales of streamwise velocity fluctuations. A conditional analysis around the occurrence of strong mobilization events revealed that incipient motion is consistently preceded and accompanied by the passage of large-scale sweep-type events, characterized by positive streamwise and negative wall-normal velocity fluctuations spanning the wall-normal extent of the boundary layer. Scale-decomposed and band-passed analysis established that this organized signature is carried predominantly by scales larger than approximately 15 times the boundary-layer thickness. Examination of the conditional excess turbulent kinetic energy and Reynolds shear stress further revealed that the large-scale structures responsible for this sweep behavior are associated with an enhancement of streamwise energy production in the period preceding mobilization. In summary, the present work provided experimental evidence, in an aeolian context, that the energization of near-wall structures by large outer-region structures plays a central role in the initiation of particle motion. Following this, the dual-phase turbulent boundary layer (TBL) was investigated. The presence of mobilized particles was shown to elevate the streamwise and wall-normal turbulence intensity throughout the boundary layer, with the Reynolds shear stress showing a comparable enhancement in the outer region while remaining largely unchanged near the wall. A conditional analysis revealed that the flow-field around a single particle is associated with the presence of extended, large-scale, low-momentum structures in the streamwise velocity, with both the spatial and temporal extent of this influence growing substantially as particles penetrate deeper into the boundary layer. Scale-decomposed analysis confirmed that this signature is carried almost entirely by the large scales of the flow, with the small scales remaining largely unorganized and unaffected by the presence of a particle.
Scholarly Commons Citation
Thiruvenkitam, Vaishak, "Contributions Towards Understanding the Interaction Between Solid Particles and Wall-Turbulence" (2026). Doctoral Dissertations and Master's Theses. 1015.
https://commons.erau.edu/edt/1015
