In view of better understanding the properties of waxy crude oils of great practical importance, we study the rheological behavior evolution of model waxy suspensions during transient shear tests, and its variation with concentration in a wide range. Macroscopic tests show a strong destructuring process with the increasing imposed shear rate (starting from rest), while negligible restructuring is observed during shear rate decrease. MRI (Magnetic Resonance Imaging) velocimetry of the suspension during the same tests allow to observe that, in most of the concentration range tested, the material flows only in a limited thickness close to the inner cylinder, and the thickness of this shear-band decreases for increasing concentration but marginally evolves as the apparent shear rate is widely increased then decreased. This means that the extent of the liquid region is governed by the initial start-up flow conditions, and the apparent viscosity variations during the next steps (at other shear rate values) are not associated with an increase of the flowing region but with the evolution of the structure in the liquid region. For the specific case of the lowest wax content analyzed, the thickness of the unsheared region decreases considerably after shearing at a high shear rate. In this case the torque balance in the sample is capable of overcoming the yield stress of the unsheared region. We also show that despite very different (initial) elastic moduli and yield stresses in the solid regime (a factor of several orders of magnitude over the whole range of concentration), we essentially have the same power-law behavior of the fluid in the shear-band, even when the shear-band thickness is close to the particle size.

为了更好地理解蜡质原油的特性具有重要的实际意义，我们研究了瞬态剪切试验中蜡质悬浮液模型的流变行为演变及其在浓度范围内的变化。宏观测试表明，随着施加的剪切速率的增加（从静止开始），有很强的破坏过程，而在剪切速率降低期间观察到的重组可以忽略不计。在相同的测试过程中，通过悬浮液的MRI（磁共振成像）测速法可以观察到，在大多数测试浓度范围内，材料仅以接近内圆柱的有限厚度流动，并且该剪切带的厚度减小浓度增加，但随着表观剪切速率先大后小而略有变化。这意味着液体区域的范围受初始启动流动条件的控制，并且在后续步骤（在其他剪切速率值下）下的表观粘度变化与流动区域的增加无关，而与流动区域的增加有关。在液体区域的结构。对于所分析的最低蜡含量的特定情况，在以高剪切速率剪切后，未剪切区域的厚度显着减小。在这种情况下，样品中的扭矩平衡能够克服未剪切区域的屈服应力。我们还表明，尽管固体状态下的（初始）弹性模量和屈服应力相差很大（在整个浓度范围内都是几个数量级的因数），但我们在剪切过程中基本上具有相同的幂律特性。 -带，