diff --git a/doc/examples/internal_waves_coriolis/simul_idempotent.py b/doc/examples/internal_waves_coriolis/simul_idempotent.py
index 8d48202c8..1ebe9dd8a 100644
--- a/doc/examples/internal_waves_coriolis/simul_idempotent.py
+++ b/doc/examples/internal_waves_coriolis/simul_idempotent.py
@@ -112,7 +112,7 @@
     where $C$ is a constant of order 1.
 
     """
-    n = 2
+    n = 4
     C = 1.0
     dx = lx / nx
     U = amplitude * omega_f
diff --git a/doc/examples/simul_ns3d_forced_isotropic.py b/doc/examples/simul_ns3d_forced_isotropic.py
index 8ff4b4cf1..da541c2f0 100644
--- a/doc/examples/simul_ns3d_forced_isotropic.py
+++ b/doc/examples/simul_ns3d_forced_isotropic.py
@@ -14,7 +14,7 @@
     help="Number of grid points in the x direction.",
 )
 parser.add_argument(
-    "--t_end", type=float, default=8.0, help="End time of the simulation"
+    "--t_end", type=float, default=80.0, help="End time of the simulation"
 )
 parser.add_argument(
     "--order",
@@ -34,7 +34,7 @@
 
 params = Simul.create_default_params()
 
-params.output.sub_directory = "examples"
+params.output.sub_directory = "examples/test_iso3d"
 
 ny = nz = nx
 Lx = 3
@@ -77,8 +77,8 @@
 params.output.periods_save.spatial_means = 0.1
 params.output.periods_save.spectra = 0.1
 params.output.periods_save.spect_energy_budg = 0.1
+params.output.periods_save.kolmo_law = 0.1
 
 params.output.spectra.kzkh_periodicity = 1
-
 sim = Simul(params)
 sim.time_stepping.start()
diff --git a/fluidsim/base/output/spectra.py b/fluidsim/base/output/spectra.py
index ab1bc9447..6687caca3 100644
--- a/fluidsim/base/output/spectra.py
+++ b/fluidsim/base/output/spectra.py
@@ -165,6 +165,7 @@ def _plot_ndim(
         coef_compensate=0,
         coef_plot_k3=None,
         coef_plot_k53=None,
+        coef_plot_k43=None,
         coef_plot_k2=None,
         xlim=None,
         ylim=None,
@@ -261,6 +262,10 @@ def _plot_ndim(
             to_plot = coef_plot_k2 * ks_no0 ** (-2) * coef_norm
             ax.plot(ks, to_plot, "k:", label=r"$\propto k^{-2}$")
 
+        if coef_plot_k43 is not None:
+            to_plot = coef_plot_k43 * ks_no0 ** (-4.0/3) * coef_norm
+            ax.plot(ks, to_plot, "k:", label=r"$\propto k^{-4/3}$")
+
         if xlim is not None:
             ax.set_xlim(xlim)
 
diff --git a/fluidsim/solvers/ns3d/output/__init__.py b/fluidsim/solvers/ns3d/output/__init__.py
index 460bc576e..8c1a92645 100644
--- a/fluidsim/solvers/ns3d/output/__init__.py
+++ b/fluidsim/solvers/ns3d/output/__init__.py
@@ -96,7 +96,7 @@ def _complete_info_solver(info_solver):
                 "module_name": "fluidsim.base.output.kolmo_law3d",
                 "class_name": "KolmoLaw",
             },
-        )
+       )
 
     @staticmethod
     def _complete_params_with_default(params, info_solver):
diff --git a/fluidsim/solvers/ns3d/output/spectra.py b/fluidsim/solvers/ns3d/output/spectra.py
index 6b864a9ab..fa5d20155 100644
--- a/fluidsim/solvers/ns3d/output/spectra.py
+++ b/fluidsim/solvers/ns3d/output/spectra.py
@@ -267,8 +267,8 @@ def _plot_times(
             to_plot = coef_plot_k53 * ks_no0 ** (-5.0 / 3) * coef_norm
             ax.plot(ks[1:], to_plot[1:], "k-.")
 
-        if coef_plot_k2 is not None:
-            to_plot = coef_plot_k2 * ks_no0 ** (-2) * coef_norm
+        if coef_plot_k1 is not None:
+            to_plot = coef_plot_k1 * ks_no0 ** (-2) * coef_norm
             ax.plot(ks[1:], to_plot[1:], "k--")
 
         if xlim is not None:
@@ -287,6 +287,7 @@ def plot1d(
         coef_plot_k3=None,
         coef_plot_k53=None,
         coef_plot_k2=None,
+        coef_plot_k43 = None,
         xlim=None,
         ylim=None,
         directions=None,
@@ -302,6 +303,7 @@ def plot1d(
             coef_plot_k3=coef_plot_k3,
             coef_plot_k53=coef_plot_k53,
             coef_plot_k2=coef_plot_k2,
+            coef_plot_k43=coef_plot_k43,
             xlim=xlim,
             ylim=ylim,
             ndim=1,