Showing papers on "Velocity gradient published in 1993"

Three-dimensional velocity structure, seismicity, and fault structure in the Parkfield Region, central California

Abstract: This study examines the three-dimensional velocity structure in a 60- by 80-km region containing the Parkfield segment of the San Andreas fault. We use local earthquake and shot P arrival times in an iterative simultaneous inversion for velocity and hypocentral parameters. Using the three-dimensional model, we relocated 5251 events that occurred from 1969 to 1991, as well as the 1966 aftershocks, and computed 664 fault plane solutions. The San Andreas fault (SAF), characterized by a sharp across-fault velocity gradient, is the primary feature in the velocity solution. There is a 5–20% lateral change in velocity over a 4-km width, the contrast being sharper where there is better resolution. The model also shows significant variations in the velocity and in the complexity of the velocity patterns along the SAF. The largest across fault velocity difference is below Middle Mountain, where a large volume of low-velocity material impinges on the SAF from the northeast. This material is inferred to be overpressured and may be key to understanding the unusual behavior in the Parkfield preparation zone. A 20-km-long high-velocity slice is imaged northeast of the SAF near Gold Hill. Its along-fault length corresponds to the length of the maximum slip in 1966. The relocated seismicity shows that the San Andreas fault is a planar vertical fault zone at seismogenic depths. Ninety percent of the fault plane solutions that are on, or near, the SAF were right-lateral strike-slip on subvertical fault planes that parallel the SAF. Thus the surface fault complexities do not appear to extend to depth and therefore do not explain the rupture character at Parkfield. At Parkfield, variations in material properties play a key role in fault segmentation and deformation style. Our observations suggest that there may be a general relation between increasing velocity and increasing ability of the rocks to store strain energy and release it as brittle failure.

Shear-induced isotropic-to-lamellar transition.

Abstract: Reciprocating shear is found to increase the isotropic-to-lamellar transition temperature in a symmetric diblock copolymer melt. The temperature at which the isotropic state becomes unstable rapidly approaches the ordering transition as the shear rate increases. Shear-induced ordering results in lamellae orientation with wave vectors directed normal to the shear and velocity gradient directions. These results are anticipated by a recent theory that accounts for the suppression of fluctuations by a symmetry breaking field in this class of weakly first-order phase transitions.

Scattering Dichroism Measurements of Flow-Induced Structure of a Shear Thickening Suspension

Abstract: Shear thickening in concentrated colloidal dispersions of sterically stabilized PMMA particles has been investigated systematically, both mechanically and optically. Two types of shear thickening were distinguished. At the highest volume fractions, a discontinuous increase of the viscosity occurs at some critical point (in either the value of the stress or the velocity gradient). A further increase of the applied stress results in an erratic flow behavior. At lower concentrations the viscosity increases more gradually and the flow remains smooth. Dichroism experiments performed on a flowing dispersion and probing the structure in the 1-2 plane of simple shear flow do not show marked differences between a dispersion sheared in the upper Newtonian region and a continuously shear thickening sample. Moreover, it was also demonstrated that the type of shear thickening has no influence on the equilibrium values of the dichroism. However, a discontinuously shear thickening sample, sheared beyond the critical conditions, shows erratic, time-dependent transitions. The relaxation of the dichroism, after cessation of the flow, shows a marked increase in time scale compared to the relaxation time for shear rates smaller than the critical value. This enhanced relaxation process suggests that the discontinuity in viscosity is associated with the formation of very large, anisotropic aggregates of particles, which relax by both disorientation and disintegration. This behavior is closely related to the relaxation of the shear stress for a sample sheared beyond the critical conditions, which also shows two relaxation mechanisms.

Flow of newtonian and non-newtonian fluids in concentric and eccentric annuli

Abstract: Three components of mean velocity and the corresponding Reynolds shear stresses have been measured in fully developed concentric and eccentric annulus flows of a Newtonian fluid at bulk-flow Reynolds numbers of 8900 and 26600 and a weakly elastic shear-thinning polymer at effective bulk-flow Reynolds numbers of 1150, 6200 and 9600. The diameter ratio was 0.5 with eccentricities of 0, 0.5 and 1.0, and the use of a Newtonian fluid of refractive index identical to that of the Perspex working section facilitated the measurements by laser velocimetry.With the Newtonian fluid, the distribution of static pressure measurements on the outer wall is shown to be linear, with friction factors for concentric-annulus flows some 8% higher than in a smooth round pipe and for the eccentric flows of eccentricities of 0.5 and 1.0 it was lower by, respectively 8 and 22.5% than that of the concentric-annulus flow. In the former case, the law of the wall was confirmed on both inner and outer walls of the annulus at both Reynolds numbers. This was also the case for the outer wall in the eccentric-annulus flows, except in the smallest gap, but the near-inner-wall flow was not represented by a logarithmic region particularly in the smallest gap. The locations of zero shear stress and zero velocity gradient were displaced by amounts which were, like the secondary flows measured in the eccentric annulus of 0.5, almost within the measurement precision. In the eccentric-annulus flow with eccentricity of 1.0, there was a secondary flow with two circulation cells on each side of the plane of symmetry and with a maximum velocity of 2.2% of the bulk velocity.The measurements with the non-Newtonian fluid were less detailed since refraction limited the flow accessible to the light beams. The average wall shear stress coefficient was similar to that for the Newtonian fluid in the laminar region of the concentric-annulus flow and higher for the two eccentric-annulus flows. Transition was extended to an effective Reynolds number well above that for the Newtonian fluid with a drag reduction of up to 63%. The near-outer-wall flows had logarithmic forms between the Newtonian curve and that of the maximum drag-reduction asymptote, and all fluctuation levels were less than those for the Newtonian fluid, particularly the radial and tangential components.

Separation speed, retention, and dispersion in asymmetrical flow field-flow fractionation as functions of channel dimensions and flow rates

Abstract: The theory for the asymmetrical flow field-flow fractionation channel was evaluated experimentally. The assumption of a constant crossflow along the channel was satisfactory. The zone-broadening theory was extended to take into a account the longitudinal diffusion and the width of the starting sample zone. In the present apparatus the longitudinal diffusion was negligible but may have to be considered for lower outlet flow rates. The axial flow velocity gradient has the advantage that the contribution by the width of the starting sample zone to the final zone width decreases

On the behavior of velocity gradient tensor invariants in direct numerical simulations of turbulence

Abstract: Studies of direct numerical simulations of incompressible, homogeneous, and inhomogeneous turbulence indicate that, in regions of high kinetic energy dissipation rate, the geometry of the local velocity gradient field has a universal character. The velocity gradient tensor satisfies the nonlinear evolution equation (dAij/dt)+AikAkj−1/3 (AmnAnm)δij=Hij where Aij=∂ui/∂xj and the tensor Hij contains terms involving the action of cross derivatives of the pressure field and viscous diffusion of Aij. The restricted Euler equation corresponding to Hij=0 can be solved in closed form [Cantwell, Phys. Fluids A 4, 782 (1992)] and the solution has the property that, for any initial condition, Aij(t) evolves to an asymptotic state of the form Aij(t)≂Kij[R(t)]1/3 where R(t) is a function which becomes singular in a finite time and Kij is a constant matrix. A number of the universal features of fine‐scale motions observed in direct numerical simulations are reproduced by Kij.In the simulation studies the first invariant...

Shear-augmented dispersion in non-Newtonian fluids

Abstract: The rate of spread of a passive species is modified by the superposition of a velocity gradient on the concentration field. Taylor (18) solved for the rate of axial dispersion in fully developed steady Newtonian flow in a straight pipe under the conditions that the dispersion be relatively steady and that longitudinal transport be controlled by convection rather than diffusion. He found that the resulting effective axial diffusivity was proportional to the square of the Peclet numberPec and inversely proportional to the molecular diffusivity. This article shows that under similar conditions in Casson and power law fluids, both simplified models for blood, and in Bingham fluids the same proportionalities are found. Solutions are presented for fully developed steady flow in a straight tube and between flat plates. The proportionality factor, however, is dependent upon the specific rheology of the fluid. For Bingham and Casson fluids, the controlling parameter is the radius of the constant-velocity core in which the shear stress does not exceed the yield stress of the fluid. For a core radius of one-tenth the radius of the tube, the effective axial diffusivity in Casson fluids is reduced to approximately 0.78 times that in a Newtonian fluid at the same flow. Using average flow conditions, it is found that the core radius/tube radius ratio iso(10−2) too(10−1) in canine arteries and veins. Even at these small values, the effective diffusivity is diminished by 5% to 18%. for power law fluids,Pec 2 dependence is again found, but with a proportionality constant dependent upon the power law exponentn. The effective diffusivity in a power law fluid relative to that in a Newtonian fluid is roughly linearly dependent onn for 0

A calibration technique for multiple-sensor hot-wire probes and its application to vorticity measurements in the wake of a circular cylinder

Abstract: A calibration technique for multiple-sensor hot-wire probes is presented. The technique, which requires minimal information about the probe geometry, is tested using a four-sensor and a twelve-sensor probe. Two data reduction algorithms are introduced. The first one assumes a uniform velocity over the probe sensing-volume and is applied to the four-sensor probe measurements. The second one assumes a uniform velocity gradient over the sensing volume of the probe. The procedure, when applied to the twelve-sensor probe, is shown to measure the velocity gradient components successfully. In both algorithms, the unknowns (velocity and velocity gradient components) are obtained by solving the resulting systems of nonlinear algebraic equations in a least-squares sense. The performances of the probes and the algorithms are tested with measurements in the wake of a circular cylinder. The statistics and spectra show that the twelve-sensor probe is successful in the simultaneous measurement of all three components of the velocity and all three components of the vorticity vectors.

Migration error in transversely isotropic media with linear velocity variation in depth

Abstract: Given the sensitivity of imaging accuracy to the velocity used in migration, migration founded (as in practice) on the erroneous assumption that a medium is isotropic can be expected to be inaccurate for steep reflectors. Here, we estimate errors in interpreted reflection time and lateral position as a function of reflector dip for transversely isotropic models in which the axis of symmetry is vertical and the medium velocity varies linearly with depth. We limit consideration to media in which ratios of the various elastic moduli are independent of depth. Tests with reflector dips up to 120 degrees on a variety of anisotropic media show errors that axe tens of wavelengths for dips beyond 90 degrees when the medium (unrealistically) is homogeneous. For a given anisotropy, the errors are smaller for inhomogeneous media; the larger the velocity gradient, the smaller the errors. For gradients that are representative of the subsurface, lateral-position errors tend to be minor for dips less than about 60 degrees, growing to two to five wavelengths as dip passes beyond 90 degrees. These errors depend on reflector depth and average velocity to the reflector only through their ratio, i.e., migrated reflection time. Migration error, which is found tomore » be unrelated to the ratio of horizontal to vertical velocity, is such that reflections with later migrated reflection times tend to be more severely over-migrated than are those with earlier ones. Over a large range of dips, migration errors that arise when anisotropy is ignored but inhomogeneity is honored tend to be considerably smaller than those encountered when inhomogeneity is ignored in migrating data from isotropic, inhomogeneous media.« less

Diffusing wave spectroscopy in inhomogeneous flows

Abstract: A theoretical study of the time-dependent correlation function of the multiply scattered light in laminar and stationary flow is presented. We study an inhomogeneous system of flow, i.e. when the strain tensor σ ij ( r ) depends on the space variables. Since in such flows the dephasing of light is space dependent, we introduce the useful function of the local density distribution of diffusion paths. We show that the time-dependent correlation function C1(t) of the scattered field is sensitive to the root mean square of velocity gradients weighted by the cloud of diffusive light paths. We establish a general formulation of C1(t) for laminar and stationary flow in the weak scattering limit kl ⪢ 1. The effects of the dimension of the inhomogeneous system and of the boundary conditions are also discussed. These results are applied to the cases of an infinitely thin and continuous sheet of vorticity, of a Rankine vortex, and of a Gaussian shaped velocity gradient.

Geometry of isothermal and isoconcentration surfaces in thermal turbulence

Abstract: The geometry of isothermal surfaces for Rayleigh–Benard convection at Rayleigh numbers R in the range 107 to 3×108 (close to the soft to hard turbulence transition) are measured. The measurements were made by imaging the color of light scattered from chiral nematic particles suspended in the fluid. Although the isotherms are multiply connected and convoluted, they do not display fractal scaling. The minimum scale for convolutions can be understood as resulting from the competition between folding and thermal diffusion. The isotherms are characterized statistically by the probability distribution of the local curvature, which may be described approximately as a stretched exponential. The distribution is essentially independent of the position and orientation of the plane of observation, and of R over the range explored. The geometry of the isotherms is compared to that of isoconcentration surfaces for dye injected into the flow; the latter do show a limited range of approximate fractal scaling because of the smaller diffusivity of the dye. The thermal measurements are supplemented by simultaneous measurements of the velocity field obtained by particle image velocimetry. Unstable waves often form on the thermal boundary layers in regions of high horizontal velocity gradient.

Concentration effects on birefringence and flow modification of semidilute polymer solutions in extensional flows

Abstract: We examine flow birefringence and flow modification effects (polymer‐induced changes in the flow field) for two‐dimensional extensional flows of polystyrene solutions at two concentrations in the semidilute regime. The concentrations of the polymer solutions are 1500 and 4500 ppm. This corresponds to ∼0.33 and 1.0×c*, the critical concentration for domain overlap of coiled polymer molecules at equilibrium. Results from a dilute 100 ppm solution of the same polymer sample are also presented for comparison. From the steady flow birefringence results, it appears that polymer chain extension is inhibited due to intermolecular interactions as the concentration is increased. In addition, inception of steady flow experiments show distinctive overshoots in birefringence. The main result of the velocity gradient measurements in this study is that the semidilute polymer solutions (1500 and 4500 ppm) show significant inhibition of high strain rates. The onset of flow modification corresponds to a critical effective ...

The kinematics of the four‐roll mill

Abstract: Numerical computations are employed to study the flow field produced by a four‐roll mill. The radius of the cylinders a, the cylinder spacing 2b, and the size 2l of the square container are varied to assess the effects on the kinematics of the flow field. It is found that a ratio of a/b=0.625 with l/b≥3.0 produces the best approximation to a pure extensional flow. With these parameter values, the extension rate remains constant with an error of less than 1% over an axial region x/b≤0.5. By contrast, the commonly accepted design a/b=0.772 suggested by Fuller and Leal [J. Polym. Sci. Polym. Phys. 19, 557 (1981)] produces a variation in extension rate of 50% over the same region. Streamline patterns and velocity gradient error contours are presented for these two designs.

Vortex-induced disturbance field in a compressible shear layer

Abstract: The disturbance field induced by a small isolated vortex in a compressible shear layer is studied using direct simulation in a convected frame. The convective Mach number, Mc, is varied from 0.1 to 1.25. The vorticity perturbation is rapidly sheared by the mean velocity gradient. The resulting disturbance pressure field is observed to decrease both in magnitude and extent with increasing Mc, becoming a narrow transverse zone for Mc≳0.8. A similar trend is seen for the perturbation velocity magnitude and for the Reynolds shear stress. By varying the vortex size, it was verified that the decrease in perturbation levels is due to the mean‐flow Mach number and not the Mach number across the vortex. At high Mc, the vortex still communicates with the edges of the shear layer, although communication in the mean‐flow direction is strongly inhibited. The growth rate of perturbation kinetic energy declines with Mc primarily due to the reduction in shear stress. For Mc≥0.6, the pressure dilatation also contributes t...

Numerical Simulations of Two-dimensional and Three-dimensional Wind Accretion Flows of an Isothermal Gas

Abstract: We present the results of two- and three-dimensional (2D) and (3D) numerical hydrodynamical calculations of accretion flows of an isothermal gas past a gravitating compact object. The calculations were performed both for a homogeneous medium and for a medium containing a transverse density or velocity gradient. We find that 2D isothermal flows exhibit the flip-flop instability (previously seen in adiabatic calculations) both in the homogeneous and the inhomogeneous cases. In the 3D case, while some unsteadiness is observed, the instability is much less violent than in 2D. We calculate (for the first time with a 3D hydrocode) the rate of accretion of mass and angular momentum from an inhomogeneous medium

The influence of instantaneous velocity gradients on turbulence properties measured with multi-sensor hot-wire probes

Abstract: The necessary assumption that the instantaneous flow field seen by hot-wire probes with two or more sensors is uniform, i.e. that all sensors are cooled by identically the same instantaneous velocity field, is often quite erroneous in highly sheared turbulent flow, such as near the wall in a turbulent boundary layer. Intense local shear layers occur, resulting in large instantaneous velocity gradients across the sensing volume of the probe. The effects of these neglected velocity gradients on the ability of a four-sensor probe, consisting of a pair of orthogonal X-arrays, to measure the three velocity and the streamwise vorticity components is assessed. This is done by determining the synthetic response of the probe to the turbulent boundary layer database of Balint et al. (1991), in which all the velocity gradients are known. The effects of neglecting the binormal components of velocity which cool each sensor are also assessed, when the probe is treated as two uncoupled X-arrays. A small improvement to the probe's coupled X-array response is found when an estimate of the mean wall-normal velocity gradient is incorporated in the response equations.

Taylor dispersion of orientable Brownian particles in unbounded homogeneous shear flows

Abstract: The physical- and orientation-space transport of non-spherical , generally non-neutrally buoyant, Brownian particles in unbounded homogeneous shear flows is analysed with the goal of studying the respective effects of the orientational degrees of freedom of such particles upon their sedimentation and dispersion rates. In particular, the present contribution concentrates on the interaction between the Taylor dispersion mechanism (arising from coupling between the orientational dependence of the particle's translational velocity and the stochastic sampling of the orientation space via rotary Brownian diffusion) and the shear velocity field. Making use of a recent extension of generalized Taylor dispersion theory to homogeneous (unbounded) shear flows, the mean transport process in physical space is modelled by a convection–diffusion problem characterized by a pair of constant phenomenological coefficients, provided that the eigenvalues of the (constant) undisturbed velocity gradient are purely imaginary. The latter phenomenological coefficients – namely, U * , the average ‘slip velocity’ vector (of the particles relative to the ambient fluid), and D * , the dispersivity dyadic or, equivalently, the pair of dyadics $\bar{\bm M}$ and D C (or $\bar{\bm D}^c$ ), the average mobility and the Taylor (or modified Taylor) dispersivity, respectively – are evaluated both asymptotically (in the respective limits of small and large rotary Peclet numbers) as well as numerically (for arbitrary Peclet numbers). It is established that (up to a scalar multiplication factor, independent of Peclet number) the anisotropic portion of the average mobility is formally equivalent to the direct diffusive contribution to the particle stress in the context of suspension rheology. The analysis focuses mainly on the case of simple shear flow. The approximate calculation in the limit of large Peclet numbers, Pe [Gt ] 1, which makes extensive use of the ‘natural coordinates’ along Jeffery orbits previously introduced by Leal & Hinch, verifies that, if the external force is non-orthogonal to the direction along which (undisturbed) fluid velocity variations occur, two of the eigenvalues of D c are proportional to Pe ; moreover, one of these O ( Pe ) eigenvalues is negative . When the external force is parallel to the latter direction, the negative eigenvalue corresponds to the principal direction of contraction in the shear velocity field; this thus relates the non-positive nature of D C to the interaction between the Taylor dispersion mechanism and the (deterministic) convection within the shear field. Explicit results for the variation of the dyadics $\bar{\bm M}$ , D c and $\bar{\bm D}^{c}$ jointly with the respective magnitude of the shear rate and the deviation of the particle geometry from a spherical shape are presented for spheroidal particles. Among other things, it is demonstrated that the proposed definition of the modified Taylor dispersivity coefficient, $\bar{\bm D}^{c}$ , does indeed yield a non-negative dyadic.

X‐ray Couette shear cell for nonequilibrium structural studies of complex fluids under flow

Abstract: We have designed and constructed a sealed, temperature‐controlled Couette‐type shear cell which allows us to carry out in situ synchrotron x‐ray scattering studies of the nonequilibrium structures of complex fluids under flow, probing lengths ranging from the nanometer to the semimacroscopic micron scale. The sealed design allows the cell to be tilted, facilitating the scanning of all directions in reciprocal space. In contrast to existing neutron shear cells, we access the shear plane containing the velocity and the velocity gradient. The temperature control of the cell enables us to carry out phase transition studies far from equilibrium. The complex fluid systems which may be studied with this cell include thermotropic and lyotropic liquid crystals, microemulsions, and polymeric fluids. Recent results on the nematic and smectic‐A phases of a liquid crystal, and the disordered bicontinuous L3 phases of surfactant membranes in the vicinity of the ordered lamellar Lα phase under flow, are presented.

Quadruple hot-wire probes in a simulated wall flow

Abstract: A method for calibration and measurement with a fourwire probe is described. The method does not require any assumption about the response of the wires and it is not necessary to know the exact probe geometry. Measurements in a two-dimensional turbulent boundary layer showed large errors in the \(\overline {\upsilon \prime w\prime } \) shear stress, although the probe had a wire arrangement practically insensitive to mean velocity gradients normal to the wall. The problem seems to be caused by the strong instantaneous spanwise velocity gradients, as suggested by the computed response of a simple probe model inserted into a numerical flow obtained by direct simulation.

Evaluation of algebraic eddy-viscosity models in three-dimensional turbulent boundary-layer flows

Abstract: ~'vw/(dW/dy) N = anisotropy constant, ——//ar r /a \ uv/(dU/dy) £/ref__ _ = reference velocity wVv, 2 _ = kinematic normal stresses —7/v, — ww, — "vw = kinematic shear stresses W^o = surface velocity of rotating cylinder a = flow angle with respect to ATFS axis of local freestream coordinates ag = mean velocity gradient vector angle with respect to the #Fs * °f tne local freestream coordinates am = measured shear stress vector angle with respect to the #FS axis of the local freestream coordinates v kinematic viscosity

Fiber-optic dual-cylindrical wave sensor for measurement of wall velocity gradient in a fluid flow.

Abstract: A Young’s fringe pattern created by two light waves emanating from a pair of slits has been used as the basis of a fiber-optic device for measuring the velocity gradients of flows near solid surfaces. This device is a variant of a dual-beam laser Doppler velocimeter, specialized to direct measurements of wall velocity gradients. A compact version of the device is described in which a fiber-polishing technique is employed for fabrication of a two-point optical source consisting of two fiber cores separated by 18 μm. The light from this source is collimated and focused on two slits that are prepared through electron-beam lithography and that are 1 μm wide and 10 μm apart. Preliminary testing of the compact probe has been successful.

Velocity Measurements within High Velocity Air-Water Jets

Abstract: High velocity turbulent jets are often used in hydraulic structures to dissipate energy and to induce or enhance airentrainment. Examples include ski jumps and bottom aeration devices. This article presents new air concentration and velocity measurements performed in the flow development region of high velocity water jets. The measurements were obtained using a two-tips conductivity probe. The data are compared with analytical air concentration profiles derived from the diffusion equation, and theoretical velocity profiles of turbulent shear layers. The results highlight that the lower jet interface defined as C = 90% coincides with the streamline of maximum velocity gradient.

Tracer dispersion in 2‐D fractures with flat and rough walls in a radial flow geometry

Abstract: Tracer dispersion is studied in a plane fracture geometry with a radial flow between closely spaced parallel walls with either two smooth surfaces or one smooth and one rough surface. An echo dispersion technique in which the fluid is first injected into the fracture during a time Tinv and then pumped back through a detector is used in the experiments and is complemented by Monte‐Carlo‐type numerical simulations. For the smooth wall case, the Taylor dispersion mechanism is dominant when longitudinal molecular diffusion is negligible: it is verified numerically and experimentally that its transition to irreversibility only depends on the ratio of Tinv to the transverse diffusion time τm across the fracture thickness. In addition, the variation of ΔT2/(4Tinvτm) with respect to Tinv/τm is the same as for a flow of parallel geometry (ΔT2 being the mean square deviation of the transit time). Longitudinal molecular diffusion increases the global dispersion like Tinv/(PeQτm) at low Peclet numbers PeQ and long times due to the longitudinal velocity gradient. When one of the walls is rough, one expects to have a geometrical dispersion locally proportional to the velocity. A corresponding linear variation of ΔT2/(4Tinvτm) with respect to √Tinv/PeQ is observed experimentally.

Spectral analysis of wall turbulence with a bicircular electrochemical probe

Abstract: The calculation of the mass flux/velocity gradient transfer function at a wall in the direction parallel to the wall and perpendicular to the mean flow direction, has been performed in linear conditions. This transfer function is relevant to the difference of the mass fluxes between two semicircular surfaces separated by an infinitely thin gap aligned with the flow direction.

Three-dimensional velocity images in Yunnan and its neighboring district

Abstract: Using the techniques of seismic tomography three-dimensional velocity images at crust and upper mantle in Yunnan province and its adjacent region have been successfully reconstructed. The results of image are: (1) The image of the velocity in the upper crust is closely related to the well-known geological structure of the surface, the Kangdian earth axis is a distinct high velocity area, and a high velocity rock stratum, which appoaching the surface of the earth, has been formed. (2) There is a low-velocity layer between 26°–31°N and 100°–104°E in deep crust, the depth of Moho discontinuity in Sichuan bass in is less than 50 km. (3) The results of seismological tomography not only reveal the lateral heterogeneity in the researched region, but also find approximately the strike of Honghe fault from the image at bottom of crust, and the velocity in both side of the fault are different obviously. (4) There is a low-velocity column within 25 km to 110 km in Tengchong region, which may be occured by upward moving of the basalt in the mantle. (5) In studied area, the thickness of the crust in west part is thicker than in southeast part. (6) From the image at bottom of the crust we can find that earthquakes with magnitude greater than 5 occurred in big velocity gradient zones, especially in transition zone between high and low velocity. There are a few earthquake in the low-velocity area. (7) We can see from Figure 6 that there still clearly exists lateral heterogeneity at 450 depth.