Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
35,306
result(s) for
"Roughness"
Sort by:
Rough and smooth
\"Compares and contrasts common rough and smooth objects, both in nature and man-made. Includes comprehension activity\"--Provided by publisher.
Book
An Investigation of Discontinuity Roughness Scale Dependency Using High-Resolution Surface Measurements
The influence of roughness on the hydro-mechanical behavior of rock discontinuities has long been recognized. As a result, several definitions and measures of roughness have been developed. According to the ISRM (Int J Rock Mech Min Sci Geomech Abstr 15(6):319–368,
1978
), discontinuity roughness comprises large-scale (waviness) and small-scale (unevenness) components. However, the division between these scales is not clear and most investigations of surface roughness have been restricted to small fracture surfaces (<1 m
2
). Hence, the large-scale components of roughness are often neglected. Furthermore, these investigations typically define roughness using two-dimensional profiles rather than three-dimensional surfaces, which can lead to biased estimates of roughness. These limitations have led to some contradictory findings regarding roughness scale dependency (scale effects). This paper aims to provide some explanation of these contradictory findings. Through the in situ digitization and analysis of two adjacent large-scale (~2 × 3 m
2
and ~2 × 2 m
2
) migmatitic-gneiss fracture surfaces, the influence of sample size on roughness estimates are investigated. In addition, the influence of measurement resolution on roughness estimates is investigated by digitizing small-scale (100 × 100 mm
2
) samples from the same fracture with varying resolution. The findings show roughness to increase as a function of the sampling window size, in contrast to what is commonly assumed. That is, the combined waviness and unevenness of a discontinuity relative to its mean plane increases with scale. Compared to the sampling window size, the resolution of surface measurements is shown to have a far greater influence on roughness estimates. This influence of measurement resolution may explain some of the contradictory roughness scale relationships that have been published previously. It is important to note that the observed decrease in shear strength with increasing scale, as observed in many prior studies, is not being questioned; rather, a clarification of the role of roughness in this phenomenon is sought.
Journal Article
Is it smooth or rough?
Discusses the properties of matter pertaining to whether an object is smooth or rough, defining both words and using examples to illustrate the differences.
Book
Determination of Joint Roughness Coefficients Using Roughness Parameters
This study used precisely digitized standard roughness profiles to determine roughness parameters such as statistical and 2D discontinuity roughness, and fractal dimensions. Our methods were based on the relationship between the joint roughness coefficient (JRC) values and roughness parameters calculated using power law equations. Statistical and 2D roughness parameters, and fractal dimensions correlated well with JRC values, and had correlation coefficients of over 0.96. However, all of these relationships have a 4th profile (JRC 6–8) that deviates by more than ±5 % from the JRC values given in the standard roughness profiles. This indicates that this profile is statistically different than the others. We suggest that fractal dimensions should be measured within the entire range of the divider, instead of merely measuring values within a suitable range. Normalized intercept values also correlated with the JRC values, similarly to the fractal dimension values discussed above. The root mean square first derivative values, roughness profile indexes, 2D roughness parameter, and fractal dimension values decreased as the sampling interval increased. However, the structure function values increased very rapidly with increasing sampling intervals. This indicates that the roughness parameters are not independent of the sampling interval, and that the different relationships between the JRC values and these roughness parameters are dependent on the sampling interval.
Journal Article
Estimation of the joint roughness coefficient (JRC) of rock joints by vector similarity measures
Accurate determination of joint roughness coefficient (JRC) of rock joints is essential for evaluating the influence of surface roughness on the shear behavior of rock joints. The JRC values of rock joints are typically measured by visual comparison against Barton’s standard JRC profiles. However, its accuracy is strongly affected by personal bias. In the present study, a new comparison method is proposed for JRC evaluation to overcome the drawback of conventional visual comparison methods based on vector similarity measures (VSMs). The feature vectors are obtained by analyzing the angular variation of line segments of both standard JRC profiles and test profiles obtained from three kinds of natural rocks with a sampling interval of 0.5 mm. The roughness similarity degrees between test profiles and standard profiles are evaluated by the Jaccard, Dice, and cosine similarity measures. The JRC values of the test profiles are then determined according to the maximum relation index based on the similarity degrees. In the present study, a comparative analysis between the VSMs method and the JRC evaluation method using different roughness parameters demonstrated that the VSMs method is effective and accurate for JRC measurement.
Journal Article
Evaluation of Urban Local-Scale Aerodynamic Parameters: Implications for the Vertical Profile of Wind Speed and for Source Areas
Nine methods to determine local-scale aerodynamic roughness length
(
z
0
)
and zero-plane displacement
(
z
d
)
are compared at three sites (within 60 m of each other) in London, UK. Methods include three anemometric (single-level high frequency observations), six morphometric (surface geometry) and one reference-based approach (look-up tables). A footprint model is used with the morphometric methods in an iterative procedure. The results are insensitive to the initial
z
d
and
z
0
estimates. Across the three sites,
z
d
varies between 5 and 45 m depending upon the method used. Morphometric methods that incorporate roughness-element height variability agree better with anemometric methods, indicating
z
d
is consistently greater than the local mean building height. Depending upon method and wind direction,
z
0
varies between 0.1 and 5 m with morphometric
z
0
consistently being 2–3 m larger than the anemometric
z
0
. No morphometric method consistently resembles the anemometric methods. Wind-speed profiles observed with Doppler lidar provide additional data with which to assess the methods. Locally determined roughness parameters are used to extrapolate wind-speed profiles to a height roughly 200 m above the canopy. Wind-speed profiles extrapolated based on morphometric methods that account for roughness-element height variability are most similar to observations. The extent of the modelled source area for measurements varies by up to a factor of three, depending upon the morphometric method used to determine
z
d
and
z
0
.
Journal Article
Analysis of thrust pad bearing under mixed-EHL regime considering combined effect of deterministic and stochastic surface roughness
This research paper focuses on evaluating the performance of a Rayleigh step bearing under thermo-mixed-EHL condition combining the effect of deterministic and stochastic surface roughness. Sinusoidal and sawtooth waveforms are considered as the deterministic roughness on the bearing’s surface, whereas stochastic roughness such as isotropic, longitudinal, and transverse roughness is considered on both interacting surfaces. The shear flow factor has been taken into consideration for the stochastic roughness of different standard deviations in roughness heights. All related equations are iteratively solved using an advanced computational algorithm. A remarkable change in the bearing’s performance is witnessed due to the combined action of deterministic and stochastic roughness. In the contact area, generated pressure is maximum in bearing having sawtooth with transverse roughness, whereas this pressure is minimum in bearing having sinusoidal with longitudinal roughness. A significant change in bearing’s performance is witnessed upon changing the value of convergence ratios, base length ratios, and roughness parameters.
Journal Article
The solution of Rough Bilevel Nonlinear Programming Problem by using Trust-Region Penalty Method
This paper, the rough bilevel nonlinear programming problem (RBNPP) is discussed taking into consideration which level is more important than the other. BNPP is transformed into a crisp unconstrained programming problem. A trust-region method is used to ensure the global convergence of the algorithm. The mechanism of solving RBNPP is presented. There are many situations of roughness in these problems are discussed. The solution procedures for solving all roughness situations are introduced based on the new proposed methodology. The definitions of solutions are defined in all different situations. Also, we show the definition of the fully optimal solution of the BNPPs. Finally, numerical examples are given to show solution procedures of a RBNPP based on the new methodology.
Journal Article
Roughness-dependent tribology effects on discontinuous shear thickening
Surface roughness affects many properties of colloids, from depletion and capillary interactions to their dispersibility and use as emulsion stabilizers. It also impacts particle–particle frictional contacts, which have recently emerged as being responsible for the discontinuous shear thickening (DST) of dense suspensions. Tribological properties of these contacts have been rarely experimentally accessed, especially for nonspherical particles. Here, we systematically tackle the effect of nanoscale surface roughness by producing a library of all-silica, raspberry-like colloids and linking their rheology to their tribology. Rougher surfaces lead to a significant anticipation of DST onset, in terms of both shear rate and solid loading. Strikingly, they also eliminate continuous thickening. DST is here due to the interlocking of asperities, which we have identified as “stick–slip” frictional contacts by measuring the sliding of the same particles via lateral force microscopy (LFM). Direct measurements of particle–particle friction therefore highlight the value of an engineering-tribology approach to tuning the thickening of suspensions.
Journal Article
A Predictive Model for the Equivalent Hydraulic Aperture of Single Fracture Using Gene Expression Programming
The accurate prediction of the equivalent hydraulic aperture (EHA) in a single fracture is of paramount importance for the investigation of fracture flow capacity. Previous studies primarily relied on fitting experimental data to obtain the EHA, failing to accurately characterize the impact of the strong nonlinearity among fracture geometric parameters on EHA. This research integrates 170 datasets of measured EHA, incorporating key geometric parameters: average mechanical aperture (
b
m
), peak roughness height (
ξ
), and the joint roughness coefficient (
JRC
). These three main geometric characteristic parameters, used as input parameters, are the primary factors influencing the EHA. The Gene Expression Programming (GEP) method was utilized to construct a model for predicting EHA (
b
h
). The developed GEP model was then compared with 6 existing empirical models, as well as 2 AI models (Random Forest (RF) and Support Vector Machine (SVM)). The results indicate that the GEP model (R
2
= 0.997) and the SVM model (R
2
= 0.9944) both demonstrate high accuracy, evidenced by the GEP model's low RMSE (0.014) and MAE (0.01) values. The sensitivity analysis indicates that in the GEP model, the hydraulic aperture increases linearly with the increase of
b
m
, decreases linearly with the increase of
ξ
, and initially increases but then decreases as JRC increases. These findings provide insightful contributions to the assessment of hydraulic conductivity in the rough single fracture.
Highlights
GEP model accurately predicts hydraulic aperture (R² = 0.997) with clear formula.
GEP model outperforms six existing empirical & two AI models in stats.
Highlights
b
m
, JRC as key in hydraulic aperture,
ξ
impact is minor.
GEP model shows complex impact of geometry on hydraulic aperture
Journal Article