diff --git a/.gitignore b/.gitignore
index d8fcca8..e828b8c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 node_modules/
 target/
 pkg/
-dist/
\ No newline at end of file
+dist/
+.DS_Store
diff --git a/index.html b/index.html
index 5f76c01..6ceb046 100644
--- a/index.html
+++ b/index.html
@@ -26,6 +26,10 @@ <h1>Eulerian Fluid Simulation</h1>
           <option value="rainbow">Rainbow</option>
           <option value="grayscale">Grayscale</option>
         </select>
+
+        <!-- slider for input velocity -->
+        <label for="in_vel">Input velocity</label>
+        <input type="range" id="in_vel" name="in_vel" min="0" max="5" value="0.8" step="0.01">
       </div>
 
       <div class="control_line">
diff --git a/index.js b/index.js
index c7da8ba..f53aad5 100644
--- a/index.js
+++ b/index.js
@@ -17,6 +17,9 @@ import('./pkg')
         // Get the streamlines_spacing slider
         const streamlines_spacing_slider = document.getElementById("streamlines_spacing");
 
+        // Get the in_vel slider
+        const in_vel_slider = document.getElementById("in_vel");
+
         // Get the colormap selector
         const colormap_selector = document.getElementById("colormap");
 
@@ -58,10 +61,12 @@ import('./pkg')
 
         const overrelaxation = 1.9;
 
-        const gravity = -9.81;
+        const gravity = 0.;
+
+        const in_vel = 0.8;
 
         // Create the fluid simulation
-        const fluid = wasm.Fluid.create(gravity, numX, numY, h, density)
+        const fluid = wasm.Fluid.create(gravity, in_vel, numX, numY, h, density)
 
         // Setup the obstacles
         fluid.clear_obstacles();
@@ -71,6 +76,7 @@ import('./pkg')
             simu_canvas, scenario_selector,
             pressure_checkbox, streamlines_checkbox,
             streamlines_num_seg_slider, streamlines_spacing_slider,
+            in_vel_slider,
             colormap_selector,
             sim_to_canvas_ratio)
 
diff --git a/src/lib.rs b/src/lib.rs
index 720508f..38f9fb1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,6 +39,7 @@ pub fn run_with_selector(
     streamlines_checkbox: web_sys::HtmlInputElement,
     streamlines_num_segs: web_sys::HtmlInputElement,
     streamlines_spacing: web_sys::HtmlInputElement,
+    in_vel: web_sys::HtmlInputElement,
     colormap_selector: web_sys::HtmlSelectElement,
     sim_to_canvas_ratio: u32,
 ) -> Result<(), JsValue> {
@@ -47,7 +48,7 @@ pub fn run_with_selector(
 
     let previous_frame = Rc::new(RefCell::new(Instant::now()));
 
-    let scenario = Rc::new(RefCell::new(None::<String>));
+    let scenario = Rc::new(RefCell::new(None::<(String, f32)>));
 
     let context = canvas
         .get_context("2d")
@@ -75,6 +76,8 @@ pub fn run_with_selector(
         let streamlines_num_segs = streamlines_num_segs.value_as_number() as usize;
         let streamlines_spacing = streamlines_spacing.value_as_number() as usize;
 
+        let in_vel = in_vel.value_as_number() as f32;
+
         let options = DrawOptions {
             pressure,
             obstacle: true,
@@ -90,27 +93,33 @@ pub fn run_with_selector(
         // If the scenario is not set or has changed, update the fluid.
         let mut scenario = scenario.borrow_mut();
         match scenario.as_ref() {
-            Some(sv) if sv == scenario_value.as_str() => {}
+            Some((sv, in_vel_)) if (sv == scenario_value.as_str()) && (*in_vel_ == in_vel) => {}
             _ => {
-                scenario.replace(scenario_value.clone());
+                scenario.replace((scenario_value.clone(), in_vel));
 
                 match scenario_value.as_str() {
                     "rectangular" => {
                         fluid.clear_obstacles();
-                        fluid.vortex_shedding(vec![ObstacleType::Rectangular {
-                            x: 0.2,
-                            y: 0.5,
-                            w: 0.1,
-                            h: 0.3,
-                        }]);
+                        fluid.vortex_shedding(
+                            in_vel,
+                            vec![ObstacleType::Rectangular {
+                                x: 0.2,
+                                y: 0.5,
+                                w: 0.1,
+                                h: 0.3,
+                            }],
+                        );
                     }
                     _ => {
                         fluid.clear_obstacles();
-                        fluid.vortex_shedding(vec![ObstacleType::Circular {
-                            x: 0.5,
-                            y: 0.5,
-                            r: 0.2,
-                        }]);
+                        fluid.vortex_shedding(
+                            in_vel,
+                            vec![ObstacleType::Circular {
+                                x: 0.5,
+                                y: 0.5,
+                                r: 0.2,
+                            }],
+                        );
                     }
                 }
             }
diff --git a/src/simu.rs b/src/simu.rs
index 3c259a3..888d62a 100644
--- a/src/simu.rs
+++ b/src/simu.rs
@@ -35,6 +35,8 @@ use web_sys::CanvasRenderingContext2d;
 pub struct Fluid {
     /// gravity
     gravity: f32,
+    /// in_vel - horizontal velocity at the inlet
+    in_vel: f32,
 
     /// density of the fluid
     density: f32,
@@ -357,10 +359,12 @@ impl Fluid {
         let r = ctx.put_image_data(&data, 0.0, 0.0);
 
         let text = format!(
-            "min: {:>8.1}\tmax: {:>8.1}\t{:>8.1} fps",
+            "min: {:>8.1}\tmax: {:>8.1}\t{:>8.1} fps\tin_vel: {:>4.2}\t gravity: {:>4.2}",
             min_p,
             max_p,
-            1. / dt
+            1. / dt,
+            self.in_vel,
+            self.gravity
         );
 
         let _ = ctx.fill_text(&text, 12., 12.);
@@ -488,12 +492,10 @@ impl Fluid {
     }
 
     /// flow in a pipe and around obstacles with no gravity
-    pub fn vortex_shedding(&mut self, obstacles: Vec<ObstacleType>) {
+    pub fn vortex_shedding(&mut self, in_vel: f32, obstacles: Vec<ObstacleType>) {
         const FLUID: f32 = 1.0;
         const OBSTACLE: f32 = 0.0;
 
-        let in_vel = 2.0;
-
         let n = self.num_y;
 
         for i in 0..self.num_x {
@@ -521,6 +523,7 @@ impl Fluid {
         }
 
         self.gravity = 0.;
+        self.in_vel = in_vel;
 
         self.add_obstacles(obstacles.into_iter().map(|x| x.into()).collect());
     }
@@ -596,7 +599,14 @@ impl Fluid {
 
 #[wasm_bindgen]
 impl Fluid {
-    pub fn create(gravity: f32, num_x: usize, num_y: usize, h: f32, density: f32) -> Fluid {
+    pub fn create(
+        gravity: f32,
+        in_vel: f32,
+        num_x: usize,
+        num_y: usize,
+        h: f32,
+        density: f32,
+    ) -> Fluid {
         let num_x = num_x + 2; // 2 border cells
         let num_y = num_y + 2;
 
@@ -611,6 +621,7 @@ impl Fluid {
         let new_m = vec![0.0; num_cells];
         Fluid {
             gravity,
+            in_vel,
             density,
             num_x,
             num_y,