Hüsnü Tözeren’s research while affiliated with Middle East Technical University and other places

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Publications (8)


Estimation of viscous dissipation inside an erythrocyte during aspirational entry into a micropipette
  • Article

July 1984

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17 Reads

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8 Citations

Biophysical Journal

H Tözeren

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A Tözeren

Viscous dissipation inside the erythrocyte during its aspirational entry into a micropipette is analyzed. The motion of the intracellular fluid is approximated by a flow into the micropipette orifice from a half space (the portion of the erythrocyte outside the micropipette). The stream function and intracellular pressure (p) in the half space are obtained as a function of radial and axial positions near the orifice. Solution of the boundary value problem for a uniform stream entering a circular hole gives p = 2 eta HQ/pi R3p, where eta H is the intracellular viscosity, Q is the total discharge, and Rp is the pipette radius. The results indicate that the moving erythrocyte membrane helps to drive the intracellular fluid into the orifice. For normal erythrocytes, p is only approximately 0.5% of the total aspiration pressure (delta P). The contribution of p to delta P, however, may become significant when there is a large increase in eta H due to a markedly elevated intracellular hemoglobin concentration or an alteration of the physical state of hemoglobin.


Boundary integral equation method for some Stokes problems

February 1984

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17 Reads

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18 Citations

International Journal for Numerical Methods in Fluids

The boundary integral equation method is a numerical technique extensively applied in the solution of boundary value problems from many different engineering fields. The starting point of the method is the formulation of an integral equation which gives the variable at any point in terms of single and double layer potentials whose densities are the values of the variable and its derivatives on the boundary. The method consists of the numerical solution of this integral equation when the field point is taken to lie on the boundary. The present paper extends the formulation of the method to Stokes flows of a collection of particles in infinite circular cylinders. This is achieved by developing matrix Green's functions for Stokes flows in cylindrical boundaries. The results are found to be in good agreement with the results of Wang and Skalak1 and Tözeren.3


Drag on Eccentrically Positioned Spheres Translating and Rotating in Tubes

April 1983

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12 Reads

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43 Citations

Journal of Fluid Mechanics

The steady motion of an eccentrically positioned sphere in a circular cylindrical tube filled with viscous fluid is considered as a regular perturbation of the axisymmetric problem. A sequence of boundary-value problems is formulated involving Stokes equations and some linear boundary conditions. Solutions of the first- and second-order problems yield the leading terms in the perturbation series of the additional drag and the torque on the spheres. The results are found to be in good agreement with the previous off-axis solutions.


Torque on Eccentric Spheres Flowing in Tubes

June 1982

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10 Reads

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25 Citations

Journal of Applied Mechanics

The steady flow of an eccentric sphere in a circular cylindrical tube filled with viscous fluid is considered as a regular perturbation of the axisymmetric problem. A sequence of boundary value problems are formulated involving Stokes equations and some linear boundary conditions. Solution of the first-order problem yields the leading term in the perturbation series of the torque on the sphere.


Flow of particles along a deformable tube

February 1982

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10 Reads

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10 Citations

Journal of Biomechanics

Slow viscous flow of rigid particles along a deformable tube of comparable diameter is considered as a possible model for some biological flows. Lubrication theory is assumed to be valid in the fluid region. The cylindrical tube is considered to be a thin elastic shell undergoing small deflections. The mean velocity of the flow is assumed to be maintained at a constant value by the application of a pressure difference over some length including the particle, or by an external force acting directly on the particle. Numerical results are obtained for the force required to maintain the motion and for the distribution of fluid pressure and thickness along the tube as a function of the diameter ratio, dimensionless velocity parameter and the shape of the particle. Effect of the bending resistance of the tube on the flow is also discussed.


Passive mechanical properties of human leukocytes

November 1981

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52 Reads

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401 Citations

Biophysical Journal

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K.L.P. Sung

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H Tözeren

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[...]

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Micropipette experiments are used to determine the rheological properties of human leukocytes. Individual cells in EDTA are subjected to a known aspiration pressure via a micropipette, and their surface deformation from the undeformed spherical shape is recorded on a television monitor. The cells are mathematically modeled as homogeneous spheres, and a standard solid viscoelastic model is found to describe accurately the deformation of the cell for small strains. These experimental and theoretical studies provide the basis for further investigations of leukocyte rheology in health and disease.


The flow of closely fitting particles in tapered tubes

December 1979

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8 Reads

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4 Citations

International Journal of Multiphase Flow

The flow of rigid spheres, truncated cones and elastic incompressible spheres in tapered tubes is investigated assuming that the Reynolds equation is valid in the fluid and the linear theory of elasticity is applicable in the solid. It is shown that leading terms in the asymptotic expansion of pressure drop in terms of minimum fluid film thickness for neutrally buoyant rigid spheres and truncated cones are of higher order of magnitude compared to the corresponding terms for the flow of these particles in circular cylindrical tubes. The effect of taper angle on pressure drop is reduced in the case of soft elastic particles because of particle deformations and significant velocities at the particle surface.


The steady flow of closely fitting incompressible elastic spheres in a tube

July 1978

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15 Reads

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68 Citations

Journal of Fluid Mechanics

The steady flow of a suspension of closely fitting, neutrally buoyant, incompressible and elastic spheres through a circular cylindrical tube is investigated under the assumption that lubrication theory is valid in the fluid region. A series solution giving the displacement field of an elastic incompressible sphere under axisymmetrically distributed surface tractions is developed. It is found that, for closely fitting particles, flow properties of the suspension are strongly dependent on the shear modulus of the elastic material and the velocity of the particle.

Citations (7)


... Complementary theoretical works have been conducted by Hirschfeld et al. [29,30] to determine the cylindrical wall effects on the translating-rotating particle of arbitrary shape. Additionally, perturbative solutions for the rotation of eccentric spheres flowing in a cylindrical tube have been derived by Tözeren [31][32][33], finding a good agreement with the previous solutions. Modeling of hydrodynamic interactions involving a torus or a circular orifice [34] has been further presented [35]. ...

Reference:

Slow rotation of a spherical particle inside an elastic tube
Torque on Eccentric Spheres Flowing in Tubes
  • Citing Article
  • June 1982

Journal of Applied Mechanics

... In another study, Fitz-Gerald [11] considered a deformation model of pellets for explaining the shapes of red blood cells and how their shapes are more adjusted to fit in the vessels. T ozeren and Skalak [12] presented a model explaining the motion of spheres which are elastic and neutrally buoyant placed in a round tube in series by supposing the validation of the theory of lubrication. This model was again extended for the treatment of compressible spheres where the volume of the spheres could vary as a function of its pressure. ...

The steady flow of closely fitting incompressible elastic spheres in a tube
  • Citing Article
  • July 1978

Journal of Fluid Mechanics

... Thus, it is important to determine if the presence of bounding walls affects significantly the rotation of a particle. The slow rotations of a no-slip sphere in the vicinity of a no-slip boundary, such as inside a spherical cavity (or close to another sphere) [3,[31][32][33], near a large plane wall [3,34], and within a circular cylinder [35][36][37], have been theoretically examined. The slow rotation of a spherical particle located at the center of a spherical cavity, where the fluid slips at the particle and cavity surfaces, was analyzed and a closed-form formula for the torque exerted on the particle by the fluid was derived [38]. ...

Drag on Eccentrically Positioned Spheres Translating and Rotating in Tubes
  • Citing Article
  • April 1983

Journal of Fluid Mechanics

... on the axisymmetric Green's function of Tözeren (1984) and thus does not require discretization of the channel wall. However, in light of the asymmetric shapes reported by Kaoui et al. (2011) and others, it is unclear that the axisymmetric geometry is an accurate reflection of the actual 3D motion of vesicles in tubes. ...

Boundary integral equation method for some Stokes problems
  • Citing Article
  • February 1984

International Journal for Numerical Methods in Fluids

... In the micropipette technique, we use similar glass capillary tubes mounted horizontally (hence, no gravity effects) where the capillary action is now precisely controlled by the application of often delicate, applied micropipette pressures (10 s of micro-metres of water) to sometimes quite forceful (10 s of centimetres of water), all viewed under an inverted optical microscope. While initially developed in its current form in the early 1970s and used for studying the micromechanics of red blood cells [52][53][54][55][56][57][58][59][60] white blood cells, [61][62][63][64][65][66][67][68][69][70][71], and lipid vesicles [72][73][74][75][76][77][78][79][80][81][82][83][84], here, we review its adaptation for measurements of surface and interfacial tension at air-water surfaces, oil-water interfaces, and the equilibrium and dynamic adsorption of surfactants and lipids. ...

Estimation of viscous dissipation inside an erythrocyte during aspirational entry into a micropipette
  • Citing Article
  • July 1984

Biophysical Journal

... There have been a number of experimental techniques proposed to probe the rheological characteristics of the cell cytoplasm, including micropipette aspiration methods (Schmid-Schönbein et al. 1981), magnetic particle methods (Sato et al. 1984) and atomic force microscopy (Alcaraz et al. 2003). A recent study by one of us has explored the rheological response across a range of different timescales using optical tweezers (Hu et al. 2017), where the force required to move a bead through the cytoplasm is measured as a function of its displacement. ...

Passive mechanical properties of human leukocytes
  • Citing Article
  • November 1981

Biophysical Journal

... In [2,3,4] the motion of solid particles in an elastic tube is studied. A J o u r n a l P r e -p r o o f Journal Pre-proof detailed deformation analysis of the tube is considered in [3], which presents a model of a linearly elastic cylindrical shell and a highly elastic cylindrical membrane in contact with a perfectly solid spherical body. ...

Flow of particles along a deformable tube
  • Citing Article
  • February 1982

Journal of Biomechanics